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/services/netbird_client_update_service.py

@@ -0,0 +1,87 @@
+"""Central control of the NetBird *client* (peer) Automatic Updates feature.
+
+This is the "Settings > Clients > Automatic Updates" toggle inside each
+customer's own NetBird dashboard (netbirdio/netbird, added in v0.61.0) — not
+to be confused with updating the NetBird Docker images themselves
+(app/services/image_service.py).
+
+Talked to over the customer's NetBird Management REST API, authenticated
+with a Personal Access Token captured during initial deployment (see
+netbird_service.deploy_customer) or pasted in manually for customers
+deployed before this feature existed. Requests go over the internal Docker
+network directly to the customer's management container — never through
+their public dashboard URL.
+"""
+
+import json
+import logging
+from typing import Any
+
+import httpx
+
+logger = logging.getLogger(__name__)
+
+_TIMEOUT = 10
+
+
+def _base_url(container_prefix: str) -> str:
+    return f"http://{container_prefix}-management:80"
+
+
+async def get_current_settings(container_prefix: str, token: str) -> dict[str, Any]:
+    """Fetch the customer's current account settings.
+
+    Returns:
+        {"ok": True, "account_id": ..., "settings": {...}} on success, or
+        {"ok": False, "error": "..."} on failure.
+    """
+    base_url = _base_url(container_prefix)
+    headers = {"Authorization": f"Token {token}"}
+    try:
+        async with httpx.AsyncClient(timeout=_TIMEOUT) as client:
+            resp = await client.get(f"{base_url}/api/accounts", headers=headers)
+            if resp.status_code != 200:
+                return {"ok": False, "error": f"GET /api/accounts -> HTTP {resp.status_code}: {resp.text[:300]}"}
+            accounts = resp.json()
+            if not accounts:
+                return {"ok": False, "error": "No account returned by /api/accounts."}
+            account = accounts[0]
+            return {"ok": True, "account_id": account["id"], "settings": account.get("settings", {})}
+    except Exception as exc:
+        logger.warning("Failed to fetch NetBird account settings for %s: %s", container_prefix, exc)
+        return {"ok": False, "error": str(exc)}
+
+
+async def push_auto_update_settings(
+    container_prefix: str, token: str, version: str, always: bool
+) -> dict[str, Any]:
+    """Set the client automatic-updates version/mode for one customer.
+
+    NetBird's account PUT endpoint expects the *entire* settings object, not
+    a partial patch, so this fetches current settings first and only
+    overwrites the two auto-update fields.
+    """
+    current = await get_current_settings(container_prefix, token)
+    if not current["ok"]:
+        return current
+
+    settings = dict(current["settings"])
+    settings["auto_update_version"] = version
+    settings["auto_update_always"] = always
+
+    base_url = _base_url(container_prefix)
+    account_id = current["account_id"]
+    headers = {"Authorization": f"Token {token}", "Content-Type": "application/json"}
+    body = {"settings": settings}
+
+    try:
+        async with httpx.AsyncClient(timeout=_TIMEOUT) as client:
+            resp = await client.put(
+                f"{base_url}/api/accounts/{account_id}", headers=headers, content=json.dumps(body)
+            )
+            if resp.status_code != 200:
+                return {"ok": False, "error": f"PUT /api/accounts/{account_id} -> HTTP {resp.status_code}: {resp.text[:300]}"}
+            return {"ok": True}
+    except Exception as exc:
+        logger.warning("Failed to push NetBird auto-update settings for %s: %s", container_prefix, exc)
+        return {"ok": False, "error": str(exc)}