feat: 公共 Feed 游标分页 + 作者公开资料链路（T3-05 / D3-9 方案 B，ADR-002/017）

- GET /api/v1/feed：仅 published+public+未删，(published_at DESC, id DESC) keyset
  游标恰合 ix_posts_feed，{items,nextCursor,hasMore}，禁 OFFSET
- FeedCard 定型：author/category/title/contentPreview(200 码点截断)/coverImage
  (唯一 is_cover 行)/mediaCount/三计数(posts 冗余列)/likedByMe/bookmarkedByMe/publishedAt
- AuthorSummary 定型并回填 Post 详情（T3-04 偏差① authorId 占位闭环）：
  userId+nickname+avatarUrl；Feign 批量调 user /internal/users/profiles，
  60s 进程内 TTL 缓存，avatarAssetId 经 media.assets 只读解析后本地签名
- 降级语义：user 服务不可达/出错时 Feed/详情照常 200，作者摘要退为仅 userId，
  失败不入缓存；Feign 1s/2s 超时兜底
- compose 为 community 注入 PATBOND_USER_SERVICE_URL/PATBOND_INTERNAL_TOKEN
- 新增分页专项 8 例、卡片定型 5 例、作者链路 7 例、Feign 线路 3 例
  （community 32→55；全仓 251→282 全绿，check-secrets --all 通过）

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

patbond-community/src/test/resources/application.yml

@@ -4,3 +4,12 @@
 spring:
   application:
     name: patbond-community
+
+patbond:
+  # Feign client wiring must resolve at context start. Author-profile tests
+  # either replace the client bean with a DB-backed stub or (the wire test)
+  # override this URL with an in-test HTTP server; nothing ever calls this
+  # unroutable address.
+  user-service:
+    url: http://127.0.0.1:1
+  internal-token: test-internal-token