chore: remove unused code and suppress noisy Claude Code logs

- Delete unused files: retry.js, app-init.js, model-manager.js
- Remove duplicate error helpers from helpers.js (exist in errors.js)
- Remove unused exports from signature-cache.js, logger.js
- Remove unused frontend code: ErrorHandler methods, validators, canDelete, destroy
- Make internal functions private in thinking-utils.js
- Remove commented-out code from constants.js
- Remove deprecated .glass-panel CSS class
- Add silent handler for Claude Code event logging (/api/event_logging/batch)
- Suppress logging for /v1/messages/count_tokens (501 responses)
- Fix catch-all to use originalUrl (wildcard strips req.path)

Co-Authored-By: Claude <noreply@anthropic.com>

public/js/utils/account-actions.js

@@ -187,13 +187,3 @@ window.AccountActions.reloadAccounts = async function() {
         return { success: false, error: error.message };
     }
 };
-
-/**
- * 检查账号是否可以删除
- * 来自 Antigravity 数据库的账号（source='database'）不可删除
- * @param {object} account - 账号对象
- * @returns {boolean} true 表示可删除
- */
-window.AccountActions.canDelete = function(account) {
-    return account && account.source !== 'database';
-};