Second-pass review fixes: kill last hardcoded creds, wire get_services, dedup

Verification audit (re-run of the 6 skill lenses) confirmed the prior fixes hold
and surfaced a few misses:

Security (HIGH):
- search.py _check_smart_redirect still opened a raw pymysql connection with
  root/rootpassword (reachable on any 9-digit SSO query). Now uses the shared
  env-backed employee_connection helper.
- Deleted dead shopdb/core/services/employee_service.py (zero importers; carried
  another root/rootpassword literal). No hardcoded credentials remain in app
  logic; config.py dev defaults stay gated by ProductionConfig.validate.

Dead hook:
- get_services was implemented by the printers plugin but had no consumer (docs
  claimed otherwise). Added PluginManager.get_service(name) that resolves a
  service from enabled plugins; updated PLUGIN-HOOKS.md.

Tests:
- search disabled-plugin exclusion (the high-value gap): enabled plugin's
  hostname appears, disabled plugin's hostname drops out (searched by a hostname
  distinct from assetnumber so only the gated domain can match).
- get_service consumer test (unknown name -> None).

Simplify:
- Extract the triplicated GE_LOGO_SVG + loadLogo + drawLogoOverlay into shared
  frontend/src/views/print/qrLogo.js (renderQrDataUrl); both QR views use it.
- applications.py: lift the misplaced pagination import to the top; drop unused
  Computer unpacking in the 3 endpoints that only touch ComputerInstalledApp.

154 tests pass, naming/style green, app boots, QR render verified.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

shopdb/plugins/__init__.py

@@ -317,6 +317,25 @@ class PluginManager:
         """Get all loaded plugins."""
         return self.loader.get_all_loaded()
 
+    def get_service(self, name: str):
+        """Resolve a service exposed by an enabled plugin via get_services().
+
+        Consumer for the BasePlugin.get_services hook: searches enabled plugins
+        for one that registers `name` and returns the registered value (a service
+        class or factory). Returns None if no enabled plugin provides it. This is
+        how one plugin obtains another's service (e.g. the Zabbix service).
+        """
+        for plugin_name, plugin in self.get_all_plugins().items():
+            if not self.registry.is_enabled(plugin_name):
+                continue
+            try:
+                services = plugin.get_services() or {}
+            except Exception:
+                continue
+            if name in services:
+                return services[name]
+        return None
+
 
 # Global plugin manager instance
 plugin_manager = PluginManager()