storage: multi-storage management with per-storage quota

Replace the single fixed /records path with a list of storages and an
active selection (where new recordings go). Quota is now per-storage.

- config: StorageItem(id,name,type,path,quota_gb,nas-meta) + Storage keeps
  global retention_days/segment_seconds; active + items. Migration from the
  old single {path,quota_gb} schema → one local item.
- recorder: write to the active storage; restart_all() repoints on switch;
  NAS-not-mounted guard (never write into the container overlay).
- indexer: scan ALL storage roots so recordings survive an active switch.
- retention: enforce quota PER storage via db.total_size_under /
  oldest_recordings_under (path-prefix LIKE).
- api/storages: GET/POST/PUT/DELETE + activate + policy. NAS uses host-mount
  (backend stores SMB params, generates the mount/fstab command, reports
  ismount status). Retire old POST /api/storage.
- frontend: new "Хранилища" settings tab — table with inline per-row quota,
  add form (local folder / NAS SMB), global policy (segment + retention).
- compose: add shared ./storages:/storages root for extra local folders and
  host-mounted NAS shares.

VERSION 0.0.127.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/services/retention.py

@@ -61,20 +61,22 @@ class Retention:
         return len(old)
 
     async def _enforce_quota(self) -> int:
-        quota = self.config.storage.quota_gb * 1024 ** 3
-        if not quota:
-            return 0
+        # квота — на КАЖДОЕ хранилище отдельно (0 = без лимита). Для каждого удаляем
+        # самые старые записи ВНУТРИ него, пока его размер не уложится в его квоту.
         removed = 0
-        # удаляем самые старые, пока суммарный размер не уложится в квоту
-        while await self.db.total_size() > quota:
-            batch = await self.db.oldest_recordings(limit=20)
-            if not batch:
-                break
-            for rec in batch:
-                await self._remove(rec.id, rec.path)
-                removed += 1
-                if await self.db.total_size() <= quota:
+        for item in self.config.storage.items:
+            if not item.quota_gb:
+                continue
+            quota = item.quota_gb * 1024 ** 3
+            while await self.db.total_size_under(item.path) > quota:
+                batch = await self.db.oldest_recordings_under(item.path, limit=20)
+                if not batch:
                     break
+                for rec in batch:
+                    await self._remove(rec.id, rec.path)
+                    removed += 1
+                    if await self.db.total_size_under(item.path) <= quota:
+                        break
         return removed
 
     async def _remove(self, rec_id: int, path: str) -> None: