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/system.py

@@ -1,6 +1,7 @@
 """Системная статистика: диск хранилища, CPU, RAM, аптайм."""
 from __future__ import annotations
 
+import os
 import shutil
 import time
 
@@ -11,19 +12,31 @@ from ..config import Config
 _START = time.time()
 
 
-def system_stats(config: Config) -> dict:
-    path = config.storage.path
+def storage_disk(path: str) -> dict:
+    """Использование диска, на котором лежит path (для одного хранилища)."""
     try:
         usage = shutil.disk_usage(path)
-        disk = {
+        return {
             "total_gb": round(usage.total / 1024 ** 3, 1),
             "used_gb": round(usage.used / 1024 ** 3, 1),
             "free_gb": round(usage.free / 1024 ** 3, 1),
             "percent": round(usage.used / usage.total * 100, 1) if usage.total else 0,
         }
     except OSError:
-        disk = {"total_gb": 0, "used_gb": 0, "free_gb": 0, "percent": 0}
+        return {"total_gb": 0, "used_gb": 0, "free_gb": 0, "percent": 0}
 
+
+def is_mounted(path: str) -> bool:
+    """Точка монтирования? (для NAS — признак, что том реально подключён)."""
+    try:
+        return os.path.ismount(path)
+    except OSError:
+        return False
+
+
+def system_stats(config: Config) -> dict:
+    active = config.active_storage()
+    path = active.path
     vm = psutil.virtual_memory()
     return {
         "uptime_s": int(time.time() - _START),
@@ -32,8 +45,8 @@ def system_stats(config: Config) -> dict:
         "ram_used_gb": round(vm.used / 1024 ** 3, 1),
         "ram_total_gb": round(vm.total / 1024 ** 3, 1),
         "storage_path": path,
-        "disk": disk,
-        "quota_gb": config.storage.quota_gb,
+        "disk": storage_disk(path),
+        "quota_gb": active.quota_gb,
         "retention_days": config.storage.retention_days,
         "segment_seconds": config.storage.segment_seconds,
     }