Add categories and authors metadata to plugins

Introduces optional 'categories' and 'authors' fields to plugin manifests, updates plugin-manager.js to normalize and expose these fields, and enhances the settings UI to display plugin tags and authors. Also updates documentation and an example plugin manifest to demonstrate the new fields.

plugins/nebot/plugin.json

@@ -1,9 +1,14 @@
 {
-  "id": "ollama-chat",
+  "id": "nebot-chat",
   "name": "Nebot",
   "version": "0.1.0",
   "description": "Nebot: a floating chat panel that talks to a local/remote Ollama server and saves chats in the plugin folder.",
   "main": "main.js",
   "rendererPreload": "renderer-preload.js",
+  "categories": ["AI", "Chat", "Utilities"],
+  "authors": [
+    { "name": "Nebula Team", "email": "andrewzambazos@gmail.com" },
+    "Bobbybear007"
+  ],
   "enabled": true
 }