fix: A21 phase 1 — 352 routes async sans await → threadpool (v7.8.0)

- Conversion `async def` → `def` de TOUTES les routes dont le corps ne contient
  ni `await`, ni `async with`, ni `async for`, ni `asyncio` (scan automatique
  corps par corps sur app/ : 352 converties, 0 dangereuses, vérifié
  `asyncio`/`run_coroutine`/`.result()` absents). FastAPI exécute ces handlers
  dans son threadpool → tout leur SQLite (`get_conn()` + `conn.execute`) quitte
  l'event loop, sans changer une ligne de logique.
- Répartition : api_v2 60, dashboard 40, collections 25, board 23,
  workspace 19, wiki 17, permissions 14, api 14, main.py 6, + 35 fichiers.
- Les 4 routers prioritaires de l'audit sont couverts par ce lot :
  api_v2 60 + dashboard 40 + collections 25 + board 23 = 148 conversions
  (le reste de leurs routes attend la phase 2 : elles ont de vrais `await`).
- Reste (phase 2) : les 311 routes avec de vrais `await` → enrouler les blocs
  DB dans `await anyio.to_thread.run_sync(...)` ; pas de wrapper partagé livré
  (rien ne l'appellerait — YAGNI jusqu'au premier usage).

suite **1037/1037** (233 s) · `ruff check app tests` OK · docs à jour

app/routers/security.py

@@ -32,7 +32,7 @@ def _current_user_id(request: Request) -> int:
 
 
 @router.get("/tokens")
-async def list_tokens(request: Request):
+def list_tokens(request: Request):
     """List the current user's API tokens (prefix only, no secrets)."""
     uid = _current_user_id(request)
     with get_conn() as conn:
@@ -63,7 +63,7 @@ async def create_token(request: Request):
 
 
 @router.delete("/tokens/{token_id:int}")
-async def revoke_token(token_id: int, request: Request):
+def revoke_token(token_id: int, request: Request):
     """Revoke an API token (soft delete)."""
     uid = _current_user_id(request)
     with get_conn() as conn:
@@ -81,7 +81,7 @@ async def revoke_token(token_id: int, request: Request):
 
 
 @router.get("/sessions")
-async def list_sessions(request: Request):
+def list_sessions(request: Request):
     """List the current user's active sessions with their devices."""
     uid = _current_user_id(request)
     current_sid = SessionManager.session_id(request.cookies.get("flowdeck_session", ""))
@@ -101,7 +101,7 @@ async def list_sessions(request: Request):
 
 
 @router.post("/sessions/{sid}/revoke")
-async def revoke_session(sid: str, request: Request):
+def revoke_session(sid: str, request: Request):
     """Revoke an active session. If it's the current one, the user is logged out."""
     uid = _current_user_id(request)
     with get_conn() as conn: