Add system update feature, git-ignore local configs, and fix homepage request logging

- Exclude config.json and admin.json in .gitignore so live settings/passwords are never overwritten by git
- Auto-generate config.json and admin.json with defaults if missing
- Add config.json.example and admin.json.example reference templates
- Add System Update page (/admin/update) in Admin Console to pull updates via Git with 1 click
- Log effective page name in index.php instead of literal 'auto'
- Add extra HAProxy/PFSense proxy headers to RequestLogger::getClientIp()

admin/config/admin.json.example

@@ -0,0 +1,15 @@
+{
+    "users": [
+        {
+            "username": "admin",
+            "password_hash": "$2y$12$nUpoaCNZZFL8kOTHNC85q.dTy0hWRmPoF3dAn4GcvSXERMioYr5b6",
+            "role": "admin",
+            "created": "2025-01-01"
+        }
+    ],
+    "security": {
+        "session_timeout": 1800,
+        "max_login_attempts": 5,
+        "lockout_duration": 900
+    }
+}