feat(sync): 聊天图片本地化(message media_hash+download_message_images+local-first rendering)

- Message 模型新增 media_hash 列 (sha256 FK -> Media.media_hash)
- Alembic 迁移 e5f6a7b8c9d0_message_media_hash (batch_alter_table, SQLite/MySQL 通用)
- app/scraper/media.py:download_message_images 批量下载器，镜像 download_call_recordings
  - 候选: media_hash IS NULL AND channel IN ('wechat','whatsapp') AND type IN ('image','video','file') AND 任一 file_*_url LIKE 'http%'
  - image 类型优先 file_th_url (缩略图，小快省)，video/file 优先 file_url
  - per-row try/except + per-run tried set，失败不挂循环
- sync_message_images orchestrator 入口 + ENTITY_MESSAGE_IMAGES 常量 (提交自身 SyncRun，镜像 call_recordings)
- scheduler: _run_message_images + ENTITY_FUNCS['message_images'] + 加入 daily all job (尾部)
- MessageOut schema 暴露 media_hash 字段
- MessageBubble.vue local-first: media_hash 优先 /api/media/{hash}，否则回退 OSS file_url/file_th_url/file_hd_url
- types.ts: Message 接口添加 media_hash 字段
- 新增 test_message_images_downloader.py (6 tests, 镜像 test_recording_downloader)

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

yunkes/src/components/MessageBubble.vue

@@ -59,6 +59,19 @@ const bestMediaUrl = computed<string | undefined>(() => {
   return undefined
 })
 
+/**
+ * Local-first media src — when the backend has localized the media blob
+ * (`message.media_hash` set by the `message_images` sync pass), render via
+ * the local `/api/media/{hash}` endpoint instead of hitting yunke OSS.
+ * Returns `undefined` when no localized copy exists yet; callers fall back
+ * to `bestMediaUrl` / `imageFullUrl` (the OSS URLs) so a not-yet-localized
+ * message still renders (degraded — talks to OSS).
+ */
+const localSrc = computed<string | undefined>(() => {
+  const hash = props.message.media_hash
+  return hash ? `/api/media/${hash}` : undefined
+})
+
 const IMAGE_EXTS = new Set(['jpg', 'jpeg', 'webp', 'png', 'gif', 'bmp', 'tif', 'tiff'])
 const VIDEO_EXTS = new Set(['mp4', 'mov', 'webm', 'm4v', 'avi', 'mkv'])
 const AUDIO_EXTS = new Set(['mp3', 'amr', 'silk', 'm4a', 'aac', 'wav', 'ogg'])
@@ -88,11 +101,24 @@ const mediaKind = computed<'image' | 'video' | 'audio' | 'file' | undefined>(()
   return 'file'
 })
 
+/**
+ * Source for the rendered image / video / audio / file link. Local-first:
+ * when `media_hash` is present, serve the localized blob via
+ * `/api/media/{hash}`; otherwise fall back to the best OSS URL on the row
+ * (degraded — talks to yunke OSS directly). For images, click-to-zoom also
+ * uses the local URL when available (the localized blob is what we have).
+ */
+const mediaSrc = computed<string | undefined>(() => localSrc.value || bestMediaUrl.value)
+
 /**
  * Image preview src list — prefer the highest-fidelity http URL available so
  * click-to-zoom shows the best copy. Falls back to the displayed thumb URL.
+ * When a localized copy exists, the preview is the local URL (the localized
+ * blob is what we have on hand — typically the thumbnail, which is
+ * sufficient for chat-timeline display).
  */
 const imageFullUrl = computed<string | undefined>(() => {
+  if (localSrc.value) return localSrc.value
   const m = props.message
   for (const u of [m.file_hd_url, m.file_url, m.file_th_url]) {
     if (u && HTTP_RE.test(u)) return u
@@ -138,7 +164,7 @@ const typeTagLabel = computed(() => {
       <div v-if="mediaKind === 'image'" @click.stop>
         <el-image
           class="yk-msg__image"
-          :src="bestMediaUrl"
+          :src="mediaSrc"
           :preview-src-list="imageFullUrl ? [imageFullUrl] : []"
           :preview-teleported="true"
           fit="cover"
@@ -150,7 +176,7 @@ const typeTagLabel = computed(() => {
       <div v-else-if="mediaKind === 'video'" @click.stop>
         <video
           class="yk-msg__video"
-          :src="bestMediaUrl"
+          :src="mediaSrc"
           controls
           preload="metadata"
         />
@@ -159,7 +185,7 @@ const typeTagLabel = computed(() => {
       <!-- 1c. audio (http URL with audio extension) — native player + chip
            showing the duration when the message carries one. -->
       <div v-else-if="mediaKind === 'audio'" class="yk-msg__voice" @click.stop>
-        <audio class="yk-msg__audio" :src="bestMediaUrl" controls preload="metadata" />
+        <audio class="yk-msg__audio" :src="mediaSrc" controls preload="metadata" />
         <span v-if="message.duration" class="yk-msg__chip">
           <el-icon><Microphone /></el-icon>
           {{ formatDuration(message.duration) }}
@@ -170,7 +196,7 @@ const typeTagLabel = computed(() => {
       <div v-else-if="mediaKind === 'file'" @click.stop>
         <a
           class="yk-msg__chip yk-msg__chip--download"
-          :href="bestMediaUrl"
+          :href="mediaSrc"
           target="_blank"
           rel="noopener"
         >