Add GET_CONTENT picker support, fix account/login bugs, restyle selection UI

- Let Noo be picked as a source (Files + Photos) by other apps' native
  file/photo pickers via Android's GET_CONTENT intent, mirroring the
  existing "Share to Noo" plumbing: MainActivity.kt/PickIntentService/
  PickRequest, ServerProvider.pickRequest/confirmPick/cancelPick, and
  pick-mode tap handling in FilesView/PhotosView. While picking, the
  bottom nav and MoreTabsButton are restricted to Files/Photos only.
- Fix two account bugs: testConnection() failures no longer delete a
  still-valid stored app password (only an actual 401 does), and
  switchAccount() now retries a nominally-active-but-logged-out account
  instead of no-op'ing - both were silently locking users out of "Continue
  as" with no way back in except removing and re-adding the account
  (now exposed via login_view.dart's inline remove button).
- Fix the login WebView: clear cookies before every load so "Add Account"
  can't silently reuse an existing session, and push it as a
  non-animated route to avoid a known WebView-as-PlatformView black-screen-
  on-pop issue under Impeller.
- Redesign the Files/Photos selection toolbar to take over the top app bar
  entirely (SyncedHeaderScaffold.selectionBar) instead of sitting as a
  second bar under the controls row, with a horizontally-scrollable,
  uniformly-colored actions row and the same one-shot scroll-hint nudge
  the controls row uses.
- Redesign ShareUploadView to share the same SyncedHeaderScaffold chrome
  as every tab, with the uploading-file summary (marqueed via the new
  shared MarqueeTitle widget) and upload button grouped into one
  rounded/elevated bottom sheet.
- Restyle ShareSheet to open on the same DetailsHeader every other
  per-item sheet uses, and fix a couple of small design-language drifts
  (hardcoded text style, a non-rounded icon).
- Settings' account card: icon buttons with tooltips instead of text
  buttons for refresh/logout/remove, divider removed.

android/app/src/main/AndroidManifest.xml

@@ -49,11 +49,34 @@
                 <category android:name="android.intent.category.DEFAULT"/>
                 <data android:mimeType="*/*"/>
             </intent-filter>
+            <!-- Lets Noo be picked as a source ("Google Photos", "Files", ...)
+                 from another app's own file/photo picker chooser - handled by
+                 MainActivity.kt/PickIntentService, not a plugin. A single
+                 "*/*" filter matches any mimeType the caller requests
+                 (image/*, video/*, or a generic file pick). -->
+            <intent-filter>
+                <action android:name="android.intent.action.GET_CONTENT"/>
+                <category android:name="android.intent.category.DEFAULT"/>
+                <category android:name="android.intent.category.OPENABLE"/>
+                <data android:mimeType="*/*"/>
+            </intent-filter>
         </activity>
         <service
             android:name=".ShareUploadService"
             android:exported="false"
             android:foregroundServiceType="dataSync"/>
+        <!-- Hands back the file(s) a caller picked via the GET_CONTENT filter
+             above - only the app's own cache/picker/ subfolder is exposed,
+             see file_paths.xml. -->
+        <provider
+            android:name="androidx.core.content.FileProvider"
+            android:authorities="${applicationId}.picker.fileprovider"
+            android:exported="false"
+            android:grantUriPermissions="true">
+            <meta-data
+                android:name="android.support.FILE_PROVIDER_PATHS"
+                android:resource="@xml/file_paths"/>
+        </provider>
         <!-- Don't delete the meta-data below.
              This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
         <meta-data

android/app/src/main/kotlin/dev/ayushya/noo/MainActivity.kt

@@ -1,6 +1,7 @@
 package dev.ayushya.noo
 
 import android.Manifest
+import android.content.ClipData
 import android.content.Intent
 import android.content.pm.PackageManager
 import android.net.Uri
@@ -10,11 +11,13 @@ import android.os.Looper
 import android.provider.OpenableColumns
 import androidx.core.app.ActivityCompat
 import androidx.core.content.ContextCompat
+import androidx.core.content.FileProvider
 import io.flutter.embedding.android.FlutterFragmentActivity
 import io.flutter.embedding.engine.FlutterEngine
 import io.flutter.plugin.common.EventChannel
 import io.flutter.plugin.common.MethodCall
 import io.flutter.plugin.common.MethodChannel
+import java.io.File
 
 // FlutterFragmentActivity (not the default FlutterActivity) is required by
 // local_auth's Android implementation, which hosts its biometric/device
@@ -38,10 +41,17 @@ class MainActivity : FlutterFragmentActivity() {
     private val shareIntentChannelName = "dev.ayushya.noo/share_intent"
     private val newShareChannelName = "dev.ayushya.noo/share_intent/new"
     private val uploadServiceChannelName = "dev.ayushya.noo/upload_service"
+    private val pickIntentChannelName = "dev.ayushya.noo/pick_intent"
+    private val newPickChannelName = "dev.ayushya.noo/pick_intent/new"
     private val notificationPermissionRequestCode = 4202
+    // Lazy, not a field initializer - `packageName` reads through the
+    // Activity's base Context, which isn't attached yet while this class's
+    // fields are being constructed (crashes with an NPE if evaluated then).
+    private val pickerFileProviderAuthority by lazy { "$packageName.picker.fileprovider" }
 
     private val mainHandler = Handler(Looper.getMainLooper())
     private var newShareSink: EventChannel.EventSink? = null
+    private var newPickSink: EventChannel.EventSink? = null
 
     override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
         super.configureFlutterEngine(flutterEngine)
@@ -73,6 +83,26 @@ class MainActivity : FlutterFragmentActivity() {
                     else -> result.notImplemented()
                 }
             }
+
+        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, pickIntentChannelName)
+            .setMethodCallHandler { call, result ->
+                when (call.method) {
+                    "getPickRequest" -> result.success(extractPickRequest(intent))
+                    "finishPick" -> finishPick(call, result)
+                    "cancelPick" -> cancelPick(result)
+                    else -> result.notImplemented()
+                }
+            }
+
+        EventChannel(flutterEngine.dartExecutor.binaryMessenger, newPickChannelName)
+            .setStreamHandler(object : EventChannel.StreamHandler {
+                override fun onListen(arguments: Any?, events: EventChannel.EventSink) {
+                    newPickSink = events
+                }
+                override fun onCancel(arguments: Any?) {
+                    newPickSink = null
+                }
+            })
     }
 
     override fun onNewIntent(intent: Intent) {
@@ -82,6 +112,10 @@ class MainActivity : FlutterFragmentActivity() {
         if (shared.isNotEmpty()) {
             mainHandler.post { newShareSink?.success(shared) }
         }
+        val pickRequest = extractPickRequest(intent)
+        if (pickRequest != null) {
+            mainHandler.post { newPickSink?.success(pickRequest) }
+        }
     }
 
     /// Cheap Uri metadata only (display name / size / mime type) via a
@@ -180,4 +214,73 @@ class MainActivity : FlutterFragmentActivity() {
         ContextCompat.startForegroundService(this, serviceIntent)
         result.success(null)
     }
+
+    /// Non-null only when this Activity was launched (or re-delivered a new
+    /// Intent) as another app's GET_CONTENT picker - the mimeType filter and
+    /// multi-select flag the caller asked for, plus a best-effort display
+    /// name for the calling app to show in the "picking mode" banner.
+    private fun extractPickRequest(intent: Intent): Map<String, Any?>? {
+        if (intent.action != Intent.ACTION_GET_CONTENT) return null
+        val mimeType = intent.type ?: "*/*"
+        val allowMultiple = intent.getBooleanExtra(Intent.EXTRA_ALLOW_MULTIPLE, false)
+        val callerPackage = callingPackage
+        val callerLabel = callerPackage?.let {
+            try {
+                val appInfo = packageManager.getApplicationInfo(it, 0)
+                packageManager.getApplicationLabel(appInfo).toString()
+            } catch (_: PackageManager.NameNotFoundException) {
+                it
+            }
+        }
+        return mapOf(
+            "mimeType" to mimeType,
+            "allowMultiple" to allowMultiple,
+            "callerLabel" to callerLabel,
+        )
+    }
+
+    /// Hands the already-downloaded local files (see PickIntentService/
+    /// ServerProvider.confirmPick - this Activity never touches the
+    /// Nextcloud server itself) back to the caller as content:// Uris
+    /// through this app's own FileProvider, then closes the picker.
+    private fun finishPick(call: MethodCall, result: MethodChannel.Result) {
+        val paths = call.argument<List<String>>("paths")
+        val mimeTypes = call.argument<List<String>>("mimeTypes") ?: emptyList()
+        if (paths.isNullOrEmpty()) {
+            result.error("no_files", "No files to return to the caller", null)
+            return
+        }
+
+        val uris = paths.map { path ->
+            FileProvider.getUriForFile(this, pickerFileProviderAuthority, File(path))
+        }
+        val resultIntent = Intent().apply {
+            addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+        }
+        // `Intent.setData()` and `.setType()` each silently null out the
+        // other field if called separately (Android framework behavior) -
+        // `setDataAndType` is the only way to have both survive on the same
+        // Intent, which every GET_CONTENT caller expects for `data`.
+        val firstMimeType = mimeTypes.getOrNull(0) ?: "*/*"
+        if (uris.size == 1) {
+            resultIntent.setDataAndType(uris[0], firstMimeType)
+        } else {
+            val clipMimeTypes = mimeTypes.ifEmpty { listOf("*/*") }.toTypedArray()
+            val clipData = ClipData("Noo picked files", clipMimeTypes, ClipData.Item(uris[0]))
+            for (i in 1 until uris.size) clipData.addItem(ClipData.Item(uris[i]))
+            resultIntent.clipData = clipData
+            // Some callers only read `data` even for a multi-item pick, so
+            // this still points at the first file as a fallback.
+            resultIntent.setDataAndType(uris[0], firstMimeType)
+        }
+        setResult(RESULT_OK, resultIntent)
+        result.success(null)
+        finish()
+    }
+
+    private fun cancelPick(result: MethodChannel.Result) {
+        setResult(RESULT_CANCELED)
+        result.success(null)
+        finish()
+    }
 }

android/app/src/main/res/xml/file_paths.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Exposes only the app's own "picker" cache subfolder as content:// Uris -
+     used to hand a file back to another app that launched Noo as a
+     GET_CONTENT picker (see PickIntentService/MainActivity.kt). -->
+<paths xmlns:android="http://schemas.android.com/apk/res/android">
+    <cache-path name="picker" path="picker/" />
+</paths>