feat: export Markdown notes (ARQ/Redis) + backup/restore BDD — v0.5.2

- Volume data/ (bind mount ./data) remplace le volume uploads nommé
  data/notes/ → .md auto-générés, data/uploads/ → médias, data/backup/ → dumps
- Service Redis (redis:7-alpine) + worker ARQ (backend-worker)
- notes_markdown.py : frontmatter YAML + contenu + pièces jointes (liens relatifs)
  Nom : YYYY-MM-DD_slug-titre_shortid.md, rotation si titre modifié
- api/notes.py : publie export_note_markdown / remove_note_markdown sur Redis
  après chaque create / update / delete / add_attachment / delete_attachment
- api/admin.py : POST /backup, GET /backups, POST /restore/{filename} (pg_dump/pg_restore)
- Backend Dockerfile : postgresql-client ; requirements : arq==0.26.1
- ConfigPage : section "Base de données" avec sauvegarde + liste + restauration

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

backend/app/workers/notes_worker.py

@@ -0,0 +1,30 @@
+from arq.connections import RedisSettings
+from sqlalchemy import select
+from sqlalchemy.orm import selectinload
+
+from app.core.config import settings
+from app.core.database import AsyncSessionLocal
+from app.models.notes import NoteItem
+from app.services.notes_markdown import delete_note_markdown, save_note_markdown
+
+
+async def export_note_markdown(ctx: dict, note_id: str) -> None:
+    async with AsyncSessionLocal() as session:
+        stmt = (
+            select(NoteItem)
+            .where(NoteItem.id == note_id)
+            .options(selectinload(NoteItem.attachments))
+        )
+        result = await session.execute(stmt)
+        note = result.scalar_one_or_none()
+        if note:
+            save_note_markdown(note)
+
+
+async def remove_note_markdown(ctx: dict, note_id: str) -> None:
+    delete_note_markdown(note_id)
+
+
+class WorkerSettings:
+    functions = [export_note_markdown, remove_note_markdown]
+    redis_settings = RedisSettings.from_dsn(settings.redis_url)