Replace receive_sharing_intent; add background upload service; fix add-account login page

Sharing a large file to Noo used to black-screen and silently kick back
to the home screen: receive_sharing_intent copies the entire shared file
into the cache dir synchronously on the main thread before Flutter even
renders, which Android's watchdog eventually kills. Replaced with
hand-rolled handling in MainActivity.kt that only ever reads cheap Uri
metadata up front (ShareIntentService), so the destination picker always
appears instantly regardless of file size.

The destination picker (ShareUploadView) now mirrors the Files tab's own
controls/filters/listing instead of a bare folder list, and the actual
prepare+upload is handed off to ShareUploadService.kt, a real Android
foreground service with a single cancellable progress notification for
the whole batch - this survives the app being closed right after the
user confirms a destination, the same guarantee a file-manager app's own
upload notification gives.

Also fixes the "add another account" login page: it used to open in
url_launcher's bare inAppWebView, which has no close button and can hide
the status bar. LoginWebViewView is a real screen this app owns instead
(package:webview_flutter), with a normal AppBar/close button/safe area,
and can now auto-close itself on successful login.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/main.dart

@@ -2,9 +2,9 @@ import 'dart:async';
 import 'package:dynamic_color/dynamic_color.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
-import 'package:receive_sharing_intent/receive_sharing_intent.dart';
 import 'models/app_tab.dart';
 import 'providers/server_provider.dart';
+import 'services/share_intent_service.dart';
 import 'theme/app_theme.dart';
 import 'views/lock_screen_view.dart';
 import 'views/login_view.dart';
@@ -112,7 +112,7 @@ class MainShellView extends StatefulWidget {
 class _MainShellViewState extends State<MainShellView> {
   late AppTab _currentTab;
   late final Map<AppTab, ScrollController> _scrollControllers;
-  StreamSubscription<List<SharedMediaFile>>? _shareSub;
+  StreamSubscription<List<SharedFileRef>>? _shareSub;
 
   @override
   void initState() {
@@ -126,29 +126,22 @@ class _MainShellViewState extends State<MainShellView> {
     _currentTab = context.read<ServerProvider>().defaultTab;
 
     // Handles both a cold start via another app's "Share to..." sheet
-    // (getInitialMedia) and a share arriving while the app is already
-    // running (getMediaStream) - the plugin guarantees the stream doesn't
-    // re-emit whatever getInitialMedia already returned.
-    ReceiveSharingIntent.instance.getInitialMedia().then(_handleSharedFiles);
-    _shareSub = ReceiveSharingIntent.instance.getMediaStream().listen(
-      _handleSharedFiles,
-    );
+    // (getInitialShare) and a share arriving while the app is already
+    // running (onNewShare). See MainActivity.kt's doc comment for why this
+    // is hand-rolled instead of the receive_sharing_intent plugin - in
+    // short, this only ever fetches cheap Uri metadata here, never a
+    // file's actual bytes, so a large shared file can't block startup.
+    ShareIntentService.getInitialShare().then(_handleSharedFiles);
+    _shareSub = ShareIntentService.onNewShare.listen(_handleSharedFiles);
   }
 
-  void _handleSharedFiles(List<SharedMediaFile> files) {
-    final uploadable = files
-        .where(
-          (f) =>
-              f.type != SharedMediaType.text && f.type != SharedMediaType.url,
-        )
-        .toList();
-    if (uploadable.isEmpty) return;
-    ReceiveSharingIntent.instance.reset();
+  void _handleSharedFiles(List<SharedFileRef> files) {
+    if (files.isEmpty) return;
     WidgetsBinding.instance.addPostFrameCallback((_) {
       if (!mounted) return;
-      Navigator.of(context).push(
-        MaterialPageRoute(builder: (_) => ShareUploadView(files: uploadable)),
-      );
+      Navigator.of(
+        context,
+      ).push(MaterialPageRoute(builder: (_) => ShareUploadView(files: files)));
     });
   }