feat(netbird): central control of client Automatic Updates across all customers

Lets the MSP admin control NetBird's own "Settings > Clients > Automatic
Updates" feature (client/peer auto-update, v0.61.0+) for every customer from
one place, instead of logging into each customer's dashboard individually.

- New deployments automatically capture a Personal Access Token during the
  existing /api/setup bootstrap call (create_pat=true), requiring
  NB_SETUP_PAT_ENABLED=true on the management container (now set by default
  in the compose template). Token is encrypted at rest per customer.
- Existing customers (deployed before this existed) can have a token pasted
  in manually from their own dashboard — verified before being stored.
- Settings > Docker Images: master default (version + force-update toggle)
  plus "Apply to All Customers" which pushes it to everyone with a token.
- Customer detail page: shows the customer's live current setting (read
  from their NetBird API, not cached) with per-customer override or
  "sync from default".
- New app/services/netbird_client_update_service.py wraps the customer's
  NetBird Management API (GET/PUT /api/accounts) for this.

app/utils/validators.py

@@ -162,6 +162,9 @@ class SystemConfigUpdate(BaseModel):
     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
+    # Master default for the NetBird client (peer) automatic-updates feature
+    netbird_client_auto_update_version: Optional[str] = Field(None, max_length=50)
+    netbird_client_auto_update_always: Optional[bool] = None
 
     @field_validator("auto_update_check_time")
     @classmethod
@@ -174,6 +177,27 @@ class SystemConfigUpdate(BaseModel):
             raise ValueError("auto_update_check_time must be in HH:MM 24h format")
         return v
 
+
+# ---------------------------------------------------------------------------
+# NetBird client (peer) automatic updates
+# ---------------------------------------------------------------------------
+class NetbirdClientAutoUpdatePayload(BaseModel):
+    """Push a client auto-update version/mode to one or all customers."""
+
+    version: str = Field(..., max_length=50, description="'latest', 'disabled', or a version e.g. '0.61.0'")
+    always: bool = False
+
+
+class NetbirdApiTokenPayload(BaseModel):
+    """Manually register a NetBird Personal Access Token for a customer.
+
+    Needed for customers deployed before automatic PAT capture existed —
+    create a PAT once in that customer's own NetBird dashboard
+    (Settings > Service Users / Personal Access Tokens) and paste it here.
+    """
+
+    token: str = Field(..., min_length=10, max_length=500)
+
     @field_validator("ssl_mode")
     @classmethod
     def validate_ssl_mode(cls, v: Optional[str]) -> Optional[str]: