feat(config): section statistiques — BDD, médias, entités

- GET /api/admin/stats : taille BDD (pg_database_size), nb+poids photos/audio
  (scan filesystem), nb notes/todos/listes (requêtes SQL directes)
- ConfigPage : grille 3 colonnes todos/notes/listes + 2 tuiles médias + ligne BDD

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/api/admin.py

@@ -4,13 +4,50 @@ from datetime import datetime
 from pathlib import Path
 from urllib.parse import urlparse
 
-from fastapi import APIRouter, HTTPException
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.config import settings
+from app.core.database import get_session
 
 router = APIRouter()
 
 
+def _dir_stats(path: Path) -> dict:
+    files = [f for f in path.rglob("*") if f.is_file() and not f.name.startswith(".")]
+    return {"count": len(files), "size_bytes": sum(f.stat().st_size for f in files)}
+
+
+@router.get("/stats")
+async def get_stats(session: AsyncSession = Depends(get_session)):
+    # Taille de la BDD
+    db_size = (await session.execute(text("SELECT pg_database_size(current_database())"))).scalar()
+
+    # Compteurs
+    notes_count = (await session.execute(text("SELECT COUNT(*) FROM notes.items"))).scalar()
+    todos_count = (await session.execute(text("SELECT COUNT(*) FROM todos.items"))).scalar()
+    lists_count = (await session.execute(text("SELECT COUNT(*) FROM shopping.lists"))).scalar()
+
+    # Médias sur le disque
+    uploads = settings.upload_path
+    photos = _dir_stats(uploads / "images" / "originals") if (uploads / "images" / "originals").exists() else {"count": 0, "size_bytes": 0}
+    audio = _dir_stats(uploads / "audio") if (uploads / "audio").exists() else {"count": 0, "size_bytes": 0}
+
+    return {
+        "db_size_bytes": db_size,
+        "media": {
+            "photos": photos,
+            "audio": audio,
+        },
+        "counts": {
+            "notes": notes_count,
+            "todos": todos_count,
+            "shopping_lists": lists_count,
+        },
+    }
+
+
 def _pg_env() -> dict:
     url = urlparse(settings.database_url.replace("+asyncpg", ""))
     env = os.environ.copy()