feat(cardav): implement POST /accounts endpoint

Add account creation route with validation. Delegates to
CardDAVSync.addAccount() which creates account and discovers
addressbooks. Returns 201 with account + addressbooks array.

Add _mockTestConnection() helper for testing CardDAV routes without
real server connections.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

server/routes/cardav.js

@@ -7,8 +7,10 @@
 import { createLogger } from '../logger.js';
 import express from 'express';
 import * as CardDAVSync from '../services/cardav-sync.js';
+import { str, collectErrors, MAX_TITLE } from '../middleware/validate.js';
 
 const log = createLogger('CardDAV');
+const MAX_URL = 500;
 const router = express.Router();
 
 /**
@@ -26,4 +28,33 @@ router.get('/accounts', async (req, res) => {
   }
 });
 
+/**
+ * POST /api/v1/contacts/cardav/accounts
+ * Neuen CardDAV Account erstellen und Addressbooks discovern.
+ * Body: { name, cardavUrl, username, password }
+ * Response: { data: { account, addressbooks } }
+ */
+router.post('/accounts', async (req, res) => {
+  try {
+    const vName     = str(req.body.name, 'Name', { max: MAX_TITLE });
+    const vUrl      = str(req.body.cardavUrl, 'CardDAV URL', { max: MAX_URL });
+    const vUsername = str(req.body.username, 'Username', { max: MAX_TITLE });
+    const vPassword = str(req.body.password, 'Password', { max: MAX_TITLE });
+    const errors = collectErrors([vName, vUrl, vUsername, vPassword]);
+    if (errors.length) return res.status(400).json({ error: errors.join(' '), code: 400 });
+
+    const result = await CardDAVSync.addAccount(
+      vName.value,
+      vUrl.value,
+      vUsername.value,
+      vPassword.value
+    );
+
+    res.status(201).json({ data: result });
+  } catch (err) {
+    log.error('Error adding CardDAV account:', err);
+    res.status(500).json({ error: 'Interner Fehler', code: 500 });
+  }
+});
+
 export default router;

server/services/cardav-sync.js

@@ -212,6 +212,11 @@ function parseBirthday(value) {
  * @returns {Promise<Object>} { ok: true, addressbooks: [...] }
  */
 async function testConnection(cardavUrl, username, password) {
+  // Use mock if set (for testing)
+  if (_testConnectionMock) {
+    return _testConnectionMock(cardavUrl, username, password);
+  }
+
   try {
     const { createDAVClient } = await import('tsdav');
     const client = await createDAVClient({
@@ -288,7 +293,16 @@ async function addAccount(name, cardavUrl, username, password) {
 
     log.info(`Added CardDAV account "${name}" with ${addressbooks.length} addressbooks.`);
 
-    return { accountId, addressbooks: addressbookData };
+    const account = {
+      id: accountId,
+      name,
+      cardavUrl,
+      username,
+      createdAt: new Date().toISOString(),
+      lastSync: null
+    };
+
+    return { account, addressbooks: addressbookData };
   } catch (err) {
     log.error('Failed to add account:', err.message);
     throw err;
@@ -869,4 +883,19 @@ export {
 
   // Helpers (exported for testing)
   parseVCard,
+  _mockTestConnection,
 };
+
+// --------------------------------------------------------
+// Test Mocking Support
+// --------------------------------------------------------
+
+let _testConnectionMock = null;
+
+/**
+ * ONLY FOR TESTING: Mock testConnection for unit tests
+ * @param {Function|null} mockFn - Mock function or null to reset
+ */
+function _mockTestConnection(mockFn) {
+  _testConnectionMock = mockFn;
+}