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/global-audio-manager.js

@@ -23,6 +23,7 @@ class GlobalAudioManager {
    * @param {Object} playerInstance - Reference to the player instance
    */
   startPlayback(playerType, uid, playerInstance = null) {
+    console.log(`[GlobalAudioManager] startPlayback called by: ${playerType} for UID: ${uid}`);
     // If the same player is already playing the same UID, allow it
     if (this.currentPlayer === playerType && this.currentUid === uid) {
       return true;