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/main.py

@@ -1,6 +1,8 @@
 from contextlib import asynccontextmanager
+from pathlib import Path
 
 from fastapi import FastAPI
+from fastapi.staticfiles import StaticFiles
 from starlette.middleware.sessions import SessionMiddleware
 
 from app.config import Settings, get_settings
@@ -65,6 +67,11 @@ def create_app(settings: Settings | None = None) -> FastAPI:
     )
     app.include_router(web_router)
     app.include_router(operations_router)
+    app.mount(
+        "/static",
+        StaticFiles(directory=str(Path(__file__).resolve().parent / "web" / "static")),
+        name="static",
+    )
 
     @app.get("/healthz")
     def healthz() -> dict[str, str]: