feat: Overhaul client-side navigation and clean up project

- Implement a unified SPA routing system in nav.js, removing all legacy and conflicting navigation scripts (router.js, inject-nav.js, fix-nav.js).
- Refactor dashboard.js to delegate all navigation handling to the new nav.js module.
- Create new modular JS files (auth.js, personal-player.js, logger.js) to improve code organization.
- Fix all navigation-related bugs, including guest access and broken footer links.
- Clean up the project root by moving development scripts and backups to a dedicated /dev directory.
- Add a .gitignore file to exclude the database, logs, and other transient files from the repository.

static/upload.js

@@ -2,7 +2,7 @@
 
 import { showToast } from "./toast.js";
 import { playBeep } from "./sound.js";
-import { logToServer } from "./app.js";
+import { logToServer } from "./logger.js";
 
 // Initialize upload system when DOM is loaded
 document.addEventListener('DOMContentLoaded', () => {