Act on the wj architectural review: races, limits, pool and contract gaps

Findings F2, F4, F5, F6, F7, F8, F9, F10, F11 and F13 from
wj-architectural-review.md. F1/F1a (the non-sargable LOWER pattern) and F3
(the warranty sync holding a pooled connection) are being handled separately
and are untouched here.

- A collector check-in that raced another for the same PC lost everything:
  the unique index on the application fingerprint raised, nothing caught it,
  and the whole check-in rolled back, discarding state, events and hardware,
  answering the agent with form copy meant for a person. The insert now runs
  in a savepoint, reconciles what the other transaction already wrote, one row
  per savepoint so a second collision skips a row rather than the batch, and
  the check-in commits with a warning. This is the shape the delete side of
  the same function already had.
- Enrollment is deliberately unauthenticated, so it now carries a per-address
  rate limit and a cap on pending requests, and the cap is a setting an admin
  can see and change. A flood can no longer bury the approval queue or grow
  the table without bound.
- The fleet alert poll no longer formats debug strings on every request.
- BusinessUnit is on the contract surface (0.34.0), so the endpoints plugin
  stops reaching into a core table with raw SQL.
- A test walks every asset type descriptor and proves the endpoint it names
  really refuses a caller without the declared permission.
- The plugin settings routes now need a permission; they were telling anyone
  which modules a site runs and where its components live.
- The connection pool is sized explicitly with a short timeout, and the
  arithmetic against the server's connection ceiling is written next to the
  worker count instead of being left to defaults nobody chose.
- Fleet alerts carry both the correct lowercase keys and the old camelCase
  pair. Trays older than 1.7.0 match keys case-sensitively and would have gone
  quiet on every PC not yet upgraded; the old pair goes when they are.
- The dev server proxy points at localhost again, with environment variables
  for the remote-box workflow, and one developer's address is out of the
  server certificate page.

shopdb/core/api/plugins.py

@@ -43,13 +43,23 @@ def list_enabled_plugins():
 
 
 @plugins_bp.route('/settings-routes', methods=['GET'])
-@jwt_required(optional=True)
+@require_permission('settings.view')
 def get_plugin_settings_routes():
     """Return settings routes contributed by all enabled plugins.
 
     Plugins can register routes to add tabs/pages to settings hubs like
     Model Catalog, Asset Config, etc. Frontend router merges these dynamically.
 
+    Gated on settings.view, the same permission list_plugins carries. It was
+    optional-auth and listed as a public read, on the stated reasoning that
+    unauthenticated pages (kiosks, TV displays) register plugin tabs before
+    login. Nothing does: the only caller in the frontend is
+    views/settings/ModelCatalogHub.vue, which sits behind requiresAuth and
+    requiresAdmin, and no kiosk route touches it. Open, it handed an anonymous
+    caller the enabled plugin list, the settings hub layout and the internal Vue
+    component paths - free reconnaissance about which modules a site runs. The
+    login page never calls this, so gating it costs nothing pre-login.
+
     Returns: { routes: [{hub, path, name, tab, component}, ...] }
     """
     pm = current_app.extensions.get('plugin_manager')