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/cache/db.dart

@@ -120,19 +120,6 @@ class SyncMetadata extends Table {
   Set<Column> get primaryKey => {id};
 }
 
-/// Single-row cache of the /api/home response (#357 follow-up). The
-/// home screen is the first thing the user sees on app open; storing
-/// the last successful HomeData as JSON lets us yield it immediately
-/// before the REST round-trip resolves, eliminating the cold-start
-/// blank on slow / remote connections. Schema 3+.
-class CachedHomeSnapshot extends Table {
-  IntColumn get id => integer().withDefault(const Constant(1))();
-  TextColumn get json => text()();
-  DateTimeColumn get updatedAt => dateTime().withDefault(currentDateAndTime)();
-  @override
-  Set<Column> get primaryKey => {id};
-}
-
 /// Single-row cache of the /api/me/history response. Mirrors the
 /// CachedHomeSnapshot pattern: opening the History tab in the Library
 /// screen yields the last-known page immediately while a fresh REST
@@ -255,7 +242,6 @@ enum CacheSource { manual, autoLiked, autoPlaylist, autoPrefetch, incidental }
   CachedPlaylistTracks,
   AudioCacheIndex,
   SyncMetadata,
-  CachedHomeSnapshot,
   CachedHistorySnapshot,
   CachedQuarantineMine,
   CachedHomeIndex,
@@ -267,7 +253,7 @@ class AppDb extends _$AppDb {
   AppDb([QueryExecutor? e]) : super(e ?? driftDatabase(name: 'minstrel_cache'));
 
   @override
-  int get schemaVersion => 10;
+  int get schemaVersion => 11;
 
   @override
   MigrationStrategy get migration => MigrationStrategy(
@@ -284,10 +270,16 @@ class AppDb extends _$AppDb {
             await customStatement('UPDATE sync_metadata SET cursor = 0');
           }
           if (from < 3) {
-            // Schema 3: cached_home_snapshot for #357 drift-first
-            // home page. No existing rows to migrate — table starts
-            // empty; the first /api/home fetch populates it.
-            await m.createTable(cachedHomeSnapshot);
+            // Schema 3: cached_home_snapshot (legacy drift-first home).
+            // The table + its homeProvider/JSON encoders were removed
+            // in #406; recreated here as raw SQL so this historical
+            // step still compiles without the generated table symbol.
+            // The from<11 step below drops it.
+            await customStatement(
+              'CREATE TABLE IF NOT EXISTS "cached_home_snapshot" '
+              '("id" INTEGER NOT NULL DEFAULT 1, "json" TEXT, '
+              '"updated_at" INTEGER, PRIMARY KEY ("id"));',
+            );
           }
           if (from < 4) {
             // Schema 4: cached_history_snapshot for drift-first
@@ -337,6 +329,15 @@ class AppDb extends _$AppDb {
             // first persist populates it.
             await m.createTable(cachedResumeState);
           }
+          if (from < 11) {
+            // Schema 11 (#406): drop the legacy cached_home_snapshot
+            // table. The home screen now renders solely from the
+            // per-item cached_home_index path; the legacy homeProvider
+            // + its JSON encoders were removed.
+            await customStatement(
+              'DROP TABLE IF EXISTS "cached_home_snapshot";',
+            );
+          }
         },
       );
 }