Migrate 25 route files to throw-based error handling

Converted routes:
- All auth routes (totp.js, keys.js, sso-gate.js)
- Recipe deployment routes (deploy.js, manage.js, index.js)
- App deployment routes
- Config routes (assets, backup, settings)
- ARR routes (config, credentials)
- Infrastructure routes (dns, services, sites, logs)
- Additional routes (browse, ca, health, license, notifications, tailscale, updates)

Changes:
- Replaced ctx.errorResponse() with throw statements
- Replaced errorResponse() with throw statements
- Added proper error imports to each file
- 400 errors → ValidationError
- 401 errors → AuthenticationError
- 403 errors → ForbiddenError
- 404 errors → NotFoundError
- 409 errors → ConflictError
- 500 errors → Handled by middleware

Result: 25 files migrated, ~150 error responses standardized

dashcaddy-api/routes/config/backup.js

@@ -3,6 +3,7 @@ const fs = require('fs');
 const path = require('path');
 const { CADDY } = require('../../constants');
 const { exists } = require('../../fs-helpers');
+const { ValidationError, AuthenticationError } = require('../errors');
 
 module.exports = function(ctx) {
   const express = require('express');
@@ -133,7 +134,7 @@ module.exports = function(ctx) {
     const backup = req.body;
 
     if (!backup || !backup.version || !backup.files) {
-      return ctx.errorResponse(res, 400, 'Invalid backup file format');
+      throw new ValidationError('Invalid backup file format');
     }
 
     const preview = {
@@ -198,7 +199,7 @@ module.exports = function(ctx) {
     const { backup, options = {}, totpCode } = req.body;
 
     if (!backup || !backup.version || !backup.files) {
-      return ctx.errorResponse(res, 400, 'Invalid backup file format');
+      throw new ValidationError('Invalid backup file format');
     }
 
     // Require TOTP verification for restores that include security-sensitive files
@@ -208,14 +209,14 @@ module.exports = function(ctx) {
     );
     if (restoresSensitive && ctx.totpConfig.enabled && ctx.totpConfig.isSetUp) {
       if (!totpCode || !/^\d{6}$/.test(totpCode)) {
-        return ctx.errorResponse(res, 400, 'TOTP code required for restoring security-sensitive files');
+        throw new ValidationError('TOTP code required for restoring security-sensitive files');
       }
       const { authenticator } = require('otplib');
       const secret = await ctx.credentialManager.retrieve('totp.secret');
       if (secret) {
         authenticator.options = { window: 1 };
         if (!authenticator.verify({ token: totpCode, secret })) {
-          return ctx.errorResponse(res, 401, '[DC-111] Invalid TOTP code');
+          throw new AuthenticationError('[DC-111] Invalid TOTP code');
         }
       }
     }