feat: restyle admin UI and add per-user sync run history

Adds a self-hosted stylesheet (no CDN dependencies) with a card-based
dashboard and color-coded status badges, and shows the last 10 sync
runs per user on the detail page.

app/db/repositories.py

@@ -204,6 +204,16 @@ class SyncRunRepository:
     def get(self, sync_run_id: int) -> SyncRun | None:
         return self.session.get(SyncRun, sync_run_id)
 
+    def list_recent_for_user(self, user_id: int, limit: int = 10) -> list[SyncRun]:
+        return list(
+            self.session.scalars(
+                select(SyncRun)
+                .where(SyncRun.user_id == user_id)
+                .order_by(SyncRun.started_at.desc())
+                .limit(limit)
+            )
+        )
+
     def finish(
         self,
         sync_run_id: int,