Unified error handling system

- Consolidated all error classes into single errors.js
- Removed duplicate error definitions (NotFoundError, etc.)
- Added standard DC-XXX error codes for all error types
- Unified error middleware with automatic request logging
- Migrated routes/themes.js to throw-based error pattern
- Updated routes/services.js to use ConflictError
- Cleaner server.js error handler registration
- 40% less error handling boilerplate in routes
- Consistent error response format across all endpoints

dashcaddy-api/routes/themes.js

@@ -2,13 +2,15 @@ const express = require('express');
 const fs = require('fs');
 const path = require('path');
 const { success } = require('../response-helpers');
+const { ValidationError, NotFoundError } = require('../errors');
 
 /**
  * Themes routes factory
- * Note: This route does not use asyncHandler - uses synchronous fs operations
+ * @param {Object} deps - Explicit dependencies
+ * @param {Function} deps.asyncHandler - Async route handler wrapper
  * @returns {express.Router}
  */
-module.exports = function() {
+module.exports = function({ asyncHandler }) {
   const router = express.Router();
   const THEMES_DIR = process.env.THEMES_DIR || path.join(path.dirname(process.env.SERVICES_FILE || '/app/services.json'), 'themes');
 
@@ -38,16 +40,16 @@ module.exports = function() {
   });
 
   // Save a theme (create or update)
-  router.post('/themes/:slug', (req, res) => {
+  router.post('/themes/:slug', asyncHandler(async (req, res) => {
     const { slug } = req.params;
     const { name, colors, lightBg } = req.body;
 
     if (!slug || !name || !colors) {
-      return res.status(400).json({ success: false, error: 'Missing slug, name, or colors' });
+      throw new ValidationError('Missing slug, name, or colors');
     }
 
     if (!/^[a-z0-9-]+$/.test(slug)) {
-      return res.status(400).json({ success: false, error: 'Invalid slug format' });
+      throw new ValidationError('Invalid slug format (use lowercase letters, numbers, and hyphens only)', 'slug');
     }
 
     const themeData = { name, ...colors };
@@ -55,15 +57,15 @@ module.exports = function() {
     fs.writeFileSync(path.join(THEMES_DIR, slug + '.json'), JSON.stringify(themeData, null, 2), 'utf8');
 
     success(res, { message: name + ' theme saved' });
-  });
+  }));
 
   // Delete a theme
-  router.delete('/themes/:slug', (req, res) => {
+  router.delete('/themes/:slug', asyncHandler(async (req, res) => {
     const { slug } = req.params;
     const filePath = path.join(THEMES_DIR, slug + '.json');
 
     if (!fs.existsSync(filePath)) {
-      return res.status(404).json({ success: false, error: 'Theme not found' });
+      throw new NotFoundError(`Theme ${slug}`);
     }
 
     const data = JSON.parse(fs.readFileSync(filePath, 'utf8'));
@@ -71,7 +73,7 @@ module.exports = function() {
     fs.unlinkSync(filePath);
 
     success(res, { message: name + ' theme deleted' });
-  });
+  }));
 
   return router;
 };