cameras: split camera enable (Вкл) from REC (record-to-disk)

Add a separate `record` field so a camera can be registered but fully
off, or on but not recording:
- enabled (Вкл): camera on/off. Disabled = no go2rtc stream (no live),
  no recording; entry is just stored. build_streams/sync_all/reconcile
  skip disabled cameras; live grid shows "камера выключена".
- record (REC): write segments to disk. Recorder runs only when
  enabled AND record.

Unified POST /api/cameras/{id}/toggle {enabled?, record?} (replaces the
/record endpoint); go2rtc is touched only when `enabled` changes, so
flipping REC doesn't blip live. Camera table gets Вкл + Запись toggle
columns; add/edit forms get both switches.

load_config migrates the old schema (no `record` key): old `enabled`
meant "record" with live always on -> enabled=True, record=old enabled.

VERSION -> 0.0.126.

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

backend/app/config.py

@@ -18,6 +18,7 @@ class Camera:
     password: str
     main_path: str
     sub_path: str | None = None
+    record: bool = True   # REC: писать на диск. enabled — камера вообще включена (live+запись)
 
     def rtsp_url(self, path: str) -> str:
         return f"rtsp://{self.user}:{self.password}@{self.ip}:554{path}"
@@ -70,27 +71,37 @@ def load_config(path: str | None = None) -> Config:
 
     storage = Storage(**(raw.get("storage") or {}))
     live = Live(**(raw.get("live") or {}))
-    cameras = [
-        Camera(
-            id=c["id"],
-            name=c.get("name", c["id"]),
-            enabled=c.get("enabled", True),
-            ip=c["ip"],
-            user=c["user"],
-            password=c["password"],
-            main_path=c["main_path"],
-            sub_path=c.get("sub_path"),
-        )
-        for c in (raw.get("cameras") or [])
-    ]
+    cameras = [_camera_from_raw(c) for c in (raw.get("cameras") or [])]
     return Config(storage=storage, live=live, cameras=cameras)
 
 
+def _camera_from_raw(c: dict) -> Camera:
+    # Миграция со старой схемы: раньше `enabled` означал «писать на диск» (live был всегда),
+    # отдельного «камера выключена» не существовало. Старый файл (без ключа record) трактуем
+    # так: запись = старый enabled, а сама камера включена. Новый файл (с record) — как есть.
+    if "record" in c:
+        enabled, record = bool(c.get("enabled", True)), bool(c["record"])
+    else:
+        enabled, record = True, bool(c.get("enabled", True))
+    return Camera(
+        id=c["id"],
+        name=c.get("name", c["id"]),
+        enabled=enabled,
+        record=record,
+        ip=c["ip"],
+        user=c["user"],
+        password=c["password"],
+        main_path=c["main_path"],
+        sub_path=c.get("sub_path"),
+    )
+
+
 def camera_to_yaml(c: Camera) -> dict:
     return {
         "id": c.id,
         "name": c.name,
         "enabled": c.enabled,
+        "record": c.record,
         "ip": c.ip,
         "user": c.user,
         "password": c.password,