feat(client): 对接详情/播放/进度续看/收藏（K1 看剧闭环）+ 三态 UI

后端接口从 6 个扩到 13 个，全部走真数据：

- 新增 api：playback_api（/app/episodes/{id}/play）、watch_api（/app/watch/*）、
  library_api（/app/favorites*）；票据从 CatalogApi 搬到 PlaybackApi
- 新增 repository：PlaybackRepository（含票据 TTL 缓存，默认 10 分钟，时钟可注入）、
  FavoriteRepository、WatchHistoryRepository 换成服务端模型（每剧一条续看记录，删掉 demoProfileId）
- PlayerLogic：起播前取票（拿不到给三态 UI，失败可重试）；accessType 驱动锁定文案，
  不在前端猜；签名地址原样交给播放器（只补 host，不动 path/query）；
  进度上报节流 5s → 10s，切集/退出/切后台各补一次，播完带 finished
- 续看定位：服务端记录里的那一集才 seek（其它集从头播），续看位置进详情/播放页时读一次
- FavoriteController：收藏以服务端为准，乐观更新 + 失败回滚；退出登录清空
- UI 三态：详情页（加载/失败可重试/空剧集 + 续看进度条 + 收藏按钮）、
  播放页（票据加载中/失败可重试/后端判定不可播）、我的页（续看失败可重试、收藏三态、最近观看）
- l10n 新增 8 个键（en/zh/id 三份）：网络/进度/收藏失败、锁定提示、续看文案等

测试：flutter test 188 全过（存量 27 个测试文件未跑红）；新增票据过期重取、进度节流、
续看定位、收藏回滚、签名 query 原样保留、真实后端端到端联调（live_watch_flow）

lib/l10n/app_en.arb

@@ -34,7 +34,13 @@
   "localDemoProfile": "Local demo profile",
   "continueWatching": "Continue Watching",
   "watchedPercent": "Watched {percent}%",
-  "@watchedPercent": {"placeholders": {"percent": {"type": "int"}}},
+  "@watchedPercent": {
+    "placeholders": {
+      "percent": {
+        "type": "int"
+      }
+    }
+  },
   "resume": "Resume",
   "history": "History",
   "watchlist": "Watchlist",
@@ -72,16 +78,40 @@
   "originalTag": "Original",
   "dramaTag": "Short drama",
   "episodeLabel": "Episode {number}",
-  "@episodeLabel": {"placeholders": {"number": {"type": "int"}}},
+  "@episodeLabel": {
+    "placeholders": {
+      "number": {
+        "type": "int"
+      }
+    }
+  },
   "exploreSeries": "Explore series",
   "episodeCount": "{count} EPISODES",
-  "@episodeCount": {"placeholders": {"count": {"type": "int"}}},
+  "@episodeCount": {
+    "placeholders": {
+      "count": {
+        "type": "int"
+      }
+    }
+  },
   "technicalDemoCount": "FREE PREVIEW · {count} EPISODES",
-  "@technicalDemoCount": {"placeholders": {"count": {"type": "int"}}},
+  "@technicalDemoCount": {
+    "placeholders": {
+      "count": {
+        "type": "int"
+      }
+    }
+  },
   "episodes": "Episodes",
   "watchEpisodeOne": "Watch episode 1",
   "continueEpisode": "Continue episode {number}",
-  "@continueEpisode": {"placeholders": {"number": {"type": "int"}}},
+  "@continueEpisode": {
+    "placeholders": {
+      "number": {
+        "type": "int"
+      }
+    }
+  },
   "freeTestMedia": "Same demo clip · free",
   "lockedStoreUnavailable": "Locked · store unavailable",
   "freeTestClip": "Free test clip",
@@ -89,10 +119,25 @@
   "freeSamplesNotice": "Two free samples · store setup pending",
   "demoTestMedia": "FREE · SAME DEMO CLIP",
   "episodeProgress": "EPISODE {number} / {total}",
-  "@episodeProgress": {"placeholders": {"number": {"type": "int"}, "total": {"type": "int"}}},
+  "@episodeProgress": {
+    "placeholders": {
+      "number": {
+        "type": "int"
+      },
+      "total": {
+        "type": "int"
+      }
+    }
+  },
   "testVideoNotice": "Self-generated technical test video",
   "lockedTitle": "Episode {number} is locked",
-  "@lockedTitle": {"placeholders": {"number": {"type": "int"}}},
+  "@lockedTitle": {
+    "placeholders": {
+      "number": {
+        "type": "int"
+      }
+    }
+  },
   "lockedBody": "Unlocking will be available after store and verification setup. This demo does not process payments.",
   "playbackError": "This clip could not be played.",
   "catalogError": "The catalog could not be loaded.",
@@ -180,5 +225,19 @@
   "authGateTitle": "Sign in to continue",
   "authGateMessage": "Favorites and comments need an account.",
   "authGateAction": "Sign In",
-  "cancel": "Not now"
+  "cancel": "Not now",
+  "noEpisodesYet": "No playable episodes yet.",
+  "networkError": "Network is unreachable. Please check your connection and retry.",
+  "progressError": "Your watch position could not be loaded.",
+  "favoritesError": "Your favorites could not be loaded.",
+  "favoriteToggleFailed": "Could not update favorites. Please retry.",
+  "remove": "Remove",
+  "unlockComingSoon": "Unlocking with coins is coming soon.",
+  "resumeProgress": "Resume at {position} / {total}",
+  "@resumeProgress": {
+    "placeholders": {
+      "position": {},
+      "total": {}
+    }
+  }
 }