refactor(flutter): drop legacy home snapshot path (#406)

The home screen renders solely from the per-item cached_home_index
path (proven on devices for many releases); the legacy snapshot stack
was dead weight.

- library_providers: remove homeProvider + _encodeHomeData +
  _albumToJson/_artistToJson/_trackToJson; drop now-unused dart:convert
  and models/home_data.dart imports
- metadata_prefetcher: re-point off homeIndexProvider/HomeIndex —
  pre-warm artistProvider from the rediscover/last-played artist
  sections (album/track tiles hydrate their own artist on render)
- live_events_dispatcher: homeProvider -> homeIndexProvider so live
  events still refresh the home screen
- db.dart: drop CachedHomeSnapshot (table class + @DriftDatabase
  entry); schemaVersion 10->11; from<3 createTable -> raw
  customStatement so the historical step compiles without the
  generated symbol; from<11 DROP TABLE cached_home_snapshot

No test references the removed symbols. db.g.dart regenerated by CI.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/lib/shared/live_events_dispatcher.dart

@@ -20,7 +20,7 @@
 import 'package:flutter/widgets.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
-import '../library/library_providers.dart' show homeProvider;
+import '../library/library_providers.dart' show homeIndexProvider;
 import '../quarantine/quarantine_provider.dart';
 import 'live_events_provider.dart';
 
@@ -62,8 +62,8 @@ class _LiveEventsDispatcher with WidgetsBindingObserver {
       case 'quarantine.deleted_via_lidarr':
         _ref.invalidate(myQuarantineProvider);
         // Hidden / liked / album rows referencing a deleted track may
-        // now be stale — homeProvider re-fetch refreshes the cards.
-        _ref.invalidate(homeProvider);
+        // now be stale — homeIndexProvider re-fetch refreshes the cards.
+        _ref.invalidate(homeIndexProvider);
       case 'playlist.created':
       case 'playlist.updated':
       case 'playlist.deleted':
@@ -72,7 +72,7 @@ class _LiveEventsDispatcher with WidgetsBindingObserver {
         // is reflected immediately. Detail screens that need the
         // mutated row will get a separate invalidate from their own
         // listener (filed as a follow-up).
-        _ref.invalidate(homeProvider);
+        _ref.invalidate(homeIndexProvider);
       case 'scan.run_started':
       case 'scan.run_finished':
         // Admin scan card provider lives in the admin feature folder
@@ -93,7 +93,7 @@ class _LiveEventsDispatcher with WidgetsBindingObserver {
       // own, but the re-invalidate flushes any stale data that
       // landed while the app was backgrounded.
       _ref.invalidate(myQuarantineProvider);
-      _ref.invalidate(homeProvider);
+      _ref.invalidate(homeIndexProvider);
     }
   }