Dedupe native transfer/notification code and split ServerProvider into focused controllers

Consolidates duplicated GET/PUT/notification-channel logic across
DownloadService/ShareUploadService/SyncEngine into shared Kotlin helpers,
gives upload/download real batch queueing instead of dropping a second
concurrent batch, and dedupes repeated Dart channel-argument boilerplate.

Replaces the 2300+ line ServerProvider god object with ten focused
ChangeNotifiers (SessionController, SettingsController, FilesController,
PhotosController, FavoritesController, TrashController, SharesController,
RecentController, SyncStatusController, PickController) plus ItemOperations,
a plain coordinator for cross-domain item mutations - fixing the coupling
where device-sync status, per-tab data, and global UI prefs all lived in
one object. Updates every view/widget call site accordingly and refreshes
the architecture/server/standards/styling docs to match.

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

lib/services/sync_service.dart

@@ -1,7 +1,11 @@
 import 'dart:convert';
+import 'dart:io';
 import 'package:flutter/services.dart';
+import 'package:path/path.dart' as p;
+import 'package:path_provider/path_provider.dart';
 import '../models/sync_status.dart';
-import '../providers/server_provider.dart';
+import '../providers/session_controller.dart';
+import '../providers/sync_status_controller.dart';
 
 /// A snapshot of native device-sync status - see `SyncStatusBus.kt` (the
 /// in-process pub/sub it mirrors) and `MainActivity.kt`'s `syncStatusMap`.
@@ -43,34 +47,38 @@ class SyncStatusSnapshot {
 /// Dart's job here is only to gather what the native side needs, push a
 /// fresh config whenever it changes, and listen for live status; the actual
 /// PROPFIND-walk/diff/GET/PUT engine runs entirely in Kotlin, independent
-/// of the Flutter engine.
+/// of the Flutter engine. Takes [SessionController]/[SyncStatusController]
+/// directly rather than a single god-object provider, since those are the
+/// only two domains this ever needs.
 class SyncService {
   static const _channel = MethodChannel('dev.ayushya.noo/sync_service');
   static const _statusChannel = EventChannel(
     'dev.ayushya.noo/sync_service/status',
   );
 
-  /// Cancels (if [ServerProvider.syncedPaths] is now empty) or re-enqueues
-  /// the periodic sync job with fresh account/credentials/path-list/
-  /// network-constraint data - call this any time one of those changes,
-  /// since a periodic `WorkRequest`'s input is fixed at enqueue time and
-  /// can only be updated by re-enqueueing.
-  static Future<void> reschedule(ServerProvider provider) async {
-    final accountId = provider.activeAccountId;
-    final service = provider.service;
-    final authHeader = service?.authHeaders['Authorization'];
-    if (accountId == null || service == null || authHeader == null) {
+  /// Cancels (if [SyncStatusController.syncedPaths] is now empty) or
+  /// re-enqueues the periodic sync job with fresh account/credentials/
+  /// path-list/network-constraint data - call this any time one of those
+  /// changes, since a periodic `WorkRequest`'s input is fixed at enqueue
+  /// time and can only be updated by re-enqueueing.
+  static Future<void> reschedule(
+    SessionController session,
+    SyncStatusController sync,
+  ) async {
+    final accountId = session.activeAccountId;
+    final authHeader = session.service?.authHeaders['Authorization'];
+    if (accountId == null || authHeader == null) {
       return cancel();
     }
 
-    final paths = provider.syncEverything ? ['/'] : provider.syncedPaths;
+    final paths = sync.syncEverything ? ['/'] : sync.syncedPaths;
     await _channel.invokeMethod('reschedule', {
       'accountId': accountId,
-      'serverUrl': provider.serverUrl,
-      'username': provider.username,
+      'serverUrl': session.serverUrl,
+      'username': session.username,
       'authHeader': authHeader,
       'folders': jsonEncode(paths),
-      'wifiOnly': !provider.syncOnCellular,
+      'wifiOnly': !sync.syncOnCellular,
     });
   }
 
@@ -80,27 +88,29 @@ class SyncService {
 
   /// Runs a one-off sync pass immediately (Settings' "Sync now"),
   /// independent of the periodic schedule.
-  static Future<void> syncNow(ServerProvider provider) async {
-    final accountId = provider.activeAccountId;
-    final service = provider.service;
-    final authHeader = service?.authHeaders['Authorization'];
-    if (accountId == null || service == null || authHeader == null) {
+  static Future<void> syncNow(
+    SessionController session,
+    SyncStatusController sync,
+  ) async {
+    final accountId = session.activeAccountId;
+    final authHeader = session.service?.authHeaders['Authorization'];
+    if (accountId == null || authHeader == null) {
       throw Exception('Not logged in.');
     }
 
-    final paths = provider.syncEverything ? ['/'] : provider.syncedPaths;
+    final paths = sync.syncEverything ? ['/'] : sync.syncedPaths;
     await _channel.invokeMethod('syncNow', {
       'accountId': accountId,
-      'serverUrl': provider.serverUrl,
-      'username': provider.username,
+      'serverUrl': session.serverUrl,
+      'username': session.username,
       'authHeader': authHeader,
       'folders': jsonEncode(paths),
     });
   }
 
-  /// One-shot status snapshot - used to seed [ServerProvider]'s state right
-  /// after login/account-switch, before the first [statusStream] event
-  /// arrives.
+  /// One-shot status snapshot - used to seed [SyncStatusController]'s state
+  /// right after login/account-switch, before the first [statusStream]
+  /// event arrives.
   static Future<SyncStatusSnapshot> getStatus() async {
     final result = await _channel.invokeMethod<Map<dynamic, dynamic>>(
       'getSyncStatus',
@@ -121,19 +131,16 @@ class SyncService {
   /// enqueue path the notification actions use, just triggered from Dart
   /// instead of a `PendingIntent`.
   static Future<void> resolveConflict(
-    ServerProvider provider,
+    SessionController session,
     SyncConflictInfo conflict,
     String resolution,
   ) async {
-    final service = provider.service;
-    final authHeader = service?.authHeaders['Authorization'];
-    if (service == null || authHeader == null) {
-      throw Exception('Not logged in.');
-    }
+    final authHeader = session.service?.authHeaders['Authorization'];
+    if (authHeader == null) throw Exception('Not logged in.');
     await _channel.invokeMethod('resolveConflict', {
       'accountId': conflict.accountId,
-      'serverUrl': provider.serverUrl,
-      'username': provider.username,
+      'serverUrl': session.serverUrl,
+      'username': session.username,
       'authHeader': authHeader,
       'fileId': conflict.fileId,
       'remotePath': conflict.remotePath,
@@ -141,4 +148,22 @@ class SyncService {
       'resolution': resolution,
     });
   }
+
+  /// The deterministic local mirror path for [remoteItemPath] under
+  /// account [accountId] - mirrors `SyncEngine.kt#syncRoot`'s
+  /// `<externalFilesDir>/sync/<accountId>/...` layout exactly, so this
+  /// never needs to read native sync state. Returns null if nothing's
+  /// actually been synced there yet.
+  static Future<String?> localSyncedFilePath(
+    String accountId,
+    String remoteItemPath,
+  ) async {
+    final base = await getExternalStorageDirectory();
+    if (base == null) return null;
+    final relPath = remoteItemPath.startsWith('/')
+        ? remoteItemPath.substring(1)
+        : remoteItemPath;
+    final file = File(p.join(base.path, 'sync', accountId, relPath));
+    return file.existsSync() ? file.path : null;
+  }
 }