fix(monitoring): repair silent-false-positive update badge + auto-update scheduling

Customer container status checks looked up containers by an exact expected
name. When a docker compose recreate got interrupted (e.g. a hung command
previously killed the whole update-all batch on timeout), Compose could leave
the old container renamed with a random hash prefix instead of removed. The
exact-name lookup then found nothing, returned None, and that silently
counted as "up to date" (green "Aktuell") instead of surfacing as unknown —
affecting 5 customers on the appliance whose containers were actually still
running under orphaned names.

- _run_cmd no longer raises on subprocess timeout, so one stuck customer
  can't abort the rest of a batch update
- repair_container_naming() self-heals orphaned hash-renamed containers by
  renaming them back before every status check and before recreate
- update-all loop now catches per-customer exceptions instead of aborting
- status responses expose "unknown" separately from "needs_update" so the UI
  shows a distinct grey badge instead of a false-positive green one
- new settings: automatic daily update check (on/off + time), with an
  independent toggle for whether it also auto-recreates customer containers

app/utils/validators.py

@@ -158,6 +158,21 @@ class SystemConfigUpdate(BaseModel):
     git_repo_url: Optional[str] = Field(None, max_length=500)
     git_branch: Optional[str] = Field(None, max_length=100)
     git_token: Optional[str] = None  # plaintext, encrypted before storage
+    # Automatic NetBird image update check/apply
+    auto_update_check_enabled: Optional[bool] = None
+    auto_update_check_time: Optional[str] = Field(None, max_length=5)
+    auto_update_apply_enabled: Optional[bool] = None
+
+    @field_validator("auto_update_check_time")
+    @classmethod
+    def validate_auto_update_check_time(cls, v: Optional[str]) -> Optional[str]:
+        """Must be HH:MM in 24h format."""
+        if v is None:
+            return v
+        import re
+        if not re.fullmatch(r"([01]\d|2[0-3]):[0-5]\d", v):
+            raise ValueError("auto_update_check_time must be in HH:MM 24h format")
+        return v
 
     @field_validator("ssl_mode")
     @classmethod