refactor: move config_path from root into install_methods

Migrated all 80 app JSON files to place config_path inside each
install_methods object instead of at the root level. This allows
different install methods (e.g. Debian vs Alpine) to have distinct
config paths.

Also updated AGENTS.md JSON structure example to reflect the change.

AGENTS.md

@@ -781,12 +781,12 @@ Every application requires a JSON metadata file in `json/<appname>.json`.
   "documentation": "https://docs.appname.com/",
   "website": "https://appname.com/",
   "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons@main/webp/appname.webp",
-  "config_path": "/opt/appname/.env",
   "description": "Short description of the application and its purpose.",
   "install_methods": [
     {
       "type": "default",
       "script": "ct/appname.sh",
+      "config_path": "/opt/appname/.env",
       "resources": {
         "cpu": 2,
         "ram": 2048,
@@ -819,7 +819,6 @@ Every application requires a JSON metadata file in `json/<appname>.json`.
 | `documentation`       | string  | Link to official docs                              |
 | `website`             | string  | Link to official website                           |
 | `logo`                | string  | URL to application logo (preferably selfhst icons) |
-| `config_path`         | string  | Path to main config file (or empty string)         |
 | `description`         | string  | Brief description of the application               |
 | `install_methods`     | array   | Installation configurations                        |
 | `default_credentials` | object  | Default username/password (or null)                |