feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

mobile/lib/shared/community/community_storage.dart

@@ -0,0 +1,111 @@
+import 'dart:convert';
+
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+
+import 'community.dart';
+
+class CommunityStorage {
+  static const _keyCommunities = 'buzz_communities';
+  static const _keyActiveId = 'buzz_active_community_id';
+
+  // Legacy keys for migration.
+  static const _legacyCommunities = 'buzz_workspaces';
+  static const _legacyActiveId = 'buzz_active_workspace_id';
+  static const _legacyRelayUrl = 'buzz_relay_url';
+  static const _legacyToken = 'buzz_token';
+  static const _legacyPubkey = 'buzz_pubkey';
+  static const _legacyNsec = 'buzz_nsec';
+
+  final FlutterSecureStorage _secure;
+
+  CommunityStorage({FlutterSecureStorage? secure})
+    : _secure = secure ?? const FlutterSecureStorage();
+
+  /// Load all communities. On first call, migrates legacy single-community
+  /// credentials if present.
+  Future<List<Community>> loadAll() async {
+    final raw = await _secure.read(key: _keyCommunities);
+    if (raw != null) return _decodeList(raw);
+
+    final legacyCommunities = await _secure.read(key: _legacyCommunities);
+    if (legacyCommunities != null) {
+      final communities = _decodeList(legacyCommunities);
+      await _saveList(communities);
+      final legacyActiveId = await _secure.read(key: _legacyActiveId);
+      if (legacyActiveId != null) await saveActiveId(legacyActiveId);
+      await _secure.delete(key: _legacyCommunities);
+      await _secure.delete(key: _legacyActiveId);
+      return communities;
+    }
+
+    // Migration: check for legacy single-community keys.
+    final legacyUrl = await _secure.read(key: _legacyRelayUrl);
+    final legacyToken = await _secure.read(key: _legacyToken);
+    if (legacyUrl != null && legacyToken != null) {
+      final legacyPubkey = await _secure.read(key: _legacyPubkey);
+      final legacyNsec = await _secure.read(key: _legacyNsec);
+
+      final name = Community.nameFromUrl(legacyUrl);
+      final community = Community.create(
+        name: name,
+        relayUrl: legacyUrl,
+        pubkey: legacyPubkey,
+        nsec: legacyNsec,
+      );
+
+      await _saveList([community]);
+      await saveActiveId(community.id);
+
+      // Delete legacy keys.
+      await _secure.delete(key: _legacyRelayUrl);
+      await _secure.delete(key: _legacyToken);
+      await _secure.delete(key: _legacyPubkey);
+      await _secure.delete(key: _legacyNsec);
+
+      return [community];
+    }
+
+    return [];
+  }
+
+  Future<void> save(Community community) async {
+    final all = await loadAll();
+    final index = all.indexWhere((w) => w.id == community.id);
+    if (index >= 0) {
+      all[index] = community;
+    } else {
+      all.add(community);
+    }
+    await _saveList(all);
+  }
+
+  Future<void> remove(String id) async {
+    final all = await loadAll();
+    all.removeWhere((w) => w.id == id);
+    await _saveList(all);
+  }
+
+  Future<String?> loadActiveId() async {
+    return _secure.read(key: _keyActiveId);
+  }
+
+  Future<void> saveActiveId(String id) async {
+    await _secure.write(key: _keyActiveId, value: id);
+  }
+
+  Future<void> clearActiveId() async {
+    await _secure.delete(key: _keyActiveId);
+  }
+
+  List<Community> _decodeList(String raw) {
+    final list = jsonDecode(raw) as List<dynamic>;
+    return list
+        .map((entry) => Community.fromJson(entry as Map<String, dynamic>))
+        .toList();
+  }
+
+  Future<void> _saveList(List<Community> communities) async {
+    final json = jsonEncode(communities.map((item) => item.toJson()).toList());
+    await _secure.write(key: _keyCommunities, value: json);
+  }
+}