fix: 活动列表image字段统一调用resolve_url

根因: 数据库中活动image字段格式不统一，早期数据是完整URL，
新上传数据是相对路径/oss/...，桌面端直接使用导致相对路径404。

修复:
- list_activities(运营端) 对image调用resolve_url
- list_activities_public(用户端) 对image调用resolve_url
- get_event_detail(活动详情) 对image调用resolve_url
resolve_url会自动将/oss/路径转为CDN鉴权直链，完整URL原样返回

app/services/training_admin_bridge.py

@@ -62,7 +62,10 @@ def delete_course(course_id: str) -> bool:
 # ── 活动（events 表）─────────────────────────────────────────────────────
 
 def list_activities(status: str | None = None) -> list[dict]:
+    from app.infrastructure.oss import resolve_url
     rows = tdb.list_all("events", "start_at DESC")
+    for r in rows:
+        r["image"] = resolve_url(r.get("image", "") or "")
     if status:
         return [r for r in rows if r.get("status") == status]
     return rows
@@ -83,11 +86,13 @@ def create_activity(data: dict) -> dict:
 
 def list_activities_public(user_id: str | None = None, status: str | None = None) -> list[dict]:
     """公开活动列表；标注 is_mine（我发布的）与 my_registered（我已报名）。"""
+    from app.infrastructure.oss import resolve_url
     rows = tdb.list_all("events", "start_at DESC")
     bookings = tdb.list_all("bookings")
     out: list[dict] = []
     for r in rows:
         r = dict(r)
+        r["image"] = resolve_url(r.get("image", "") or "")
         r["is_mine"] = bool(user_id and r.get("publisher_id") == user_id)
         r["my_registered"] = bool(
             user_id and any(
@@ -166,10 +171,12 @@ def delete_activity_owned(event_id: str, user_id: str) -> bool:
 
 def get_event_detail(user_id: str | None, event_id: str) -> dict | None:
     """活动详情：发布者附带报名列表（bookings）；非发布者只返回活动与我的报名标记。"""
+    from app.infrastructure.oss import resolve_url
     ev = tdb.fetch_by_id("events", event_id)
     if ev is None:
         return None
     ev = dict(ev)
+    ev["image"] = resolve_url(ev.get("image", "") or "")
     is_mine = bool(user_id and ev.get("publisher_id") == user_id)
     ev["is_mine"] = is_mine
     ev["my_registered"] = False