fix: enforce consistent password policy across all auth flows

Replace duplicated inline validation with a shared validatePassword()
utility that checks minimum length (8), rejects repetitive and common
passwords, and requires uppercase, lowercase, a digit, and a special
character.

- Add server/src/services/passwordPolicy.ts as single source of truth
- Apply to registration, password change, and admin create/edit user
  (admin routes previously had zero validation)
- Fix client min-length mismatch (6 vs 8) in RegisterPage and LoginPage
- Add client-side password length guard to AdminPage forms
- Update register.passwordTooShort and settings.passwordWeak i18n keys
  in all 12 locales to reflect the corrected requirements

server/src/routes/admin.ts

@@ -10,6 +10,7 @@ import { writeAudit, getClientIp, logInfo } from '../services/auditLog';
 import { getAllPermissions, savePermissions, PERMISSION_ACTIONS } from '../services/permissions';
 import { revokeUserSessions } from '../mcp';
 import { maybe_encrypt_api_key, decrypt_api_key } from '../services/apiKeyCrypto';
+import { validatePassword } from '../services/passwordPolicy';
 import { updateJwtSecret } from '../config';
 
 const router = express.Router();
@@ -47,6 +48,9 @@ router.post('/users', (req: Request, res: Response) => {
     return res.status(400).json({ error: 'Username, email and password are required' });
   }
 
+  const pwCheck = validatePassword(password.trim());
+  if (!pwCheck.ok) return res.status(400).json({ error: pwCheck.reason });
+
   if (role && !['user', 'admin'].includes(role)) {
     return res.status(400).json({ error: 'Invalid role' });
   }
@@ -97,6 +101,10 @@ router.put('/users/:id', (req: Request, res: Response) => {
     if (conflict) return res.status(409).json({ error: 'Email already taken' });
   }
 
+  if (password) {
+    const pwCheck = validatePassword(password);
+    if (!pwCheck.ok) return res.status(400).json({ error: pwCheck.reason });
+  }
   const passwordHash = password ? bcrypt.hashSync(password, 12) : null;
 
   db.prepare(`

server/src/routes/auth.ts

@@ -10,6 +10,7 @@ import fetch from 'node-fetch';
 import { authenticator } from 'otplib';
 import QRCode from 'qrcode';
 import { db } from '../db/database';
+import { validatePassword } from '../services/passwordPolicy';
 import { authenticate, optionalAuth, demoUploadBlock } from '../middleware/auth';
 import { JWT_SECRET } from '../config';
 import { encryptMfaSecret, decryptMfaSecret } from '../services/mfaCrypto';
@@ -268,13 +269,8 @@ router.post('/register', authLimiter, (req: Request, res: Response) => {
     return res.status(400).json({ error: 'Username, email and password are required' });
   }
 
-  if (password.length < 8) {
-    return res.status(400).json({ error: 'Password must be at least 8 characters' });
-  }
-
-  if (!/[A-Z]/.test(password) || !/[a-z]/.test(password) || !/[0-9]/.test(password)) {
-    return res.status(400).json({ error: 'Password must contain at least one uppercase letter, one lowercase letter, and one number' });
-  }
+  const pwCheck = validatePassword(password);
+  if (!pwCheck.ok) return res.status(400).json({ error: pwCheck.reason });
 
   const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
   if (!emailRegex.test(email)) {
@@ -382,11 +378,8 @@ router.put('/me/password', authenticate, rateLimiter(5, RATE_LIMIT_WINDOW), (req
   const { current_password, new_password } = req.body;
   if (!current_password) return res.status(400).json({ error: 'Current password is required' });
   if (!new_password) return res.status(400).json({ error: 'New password is required' });
-  if (new_password.length < 8) return res.status(400).json({ error: 'Password must be at least 8 characters' });
-
-  if (!/[A-Z]/.test(new_password) || !/[a-z]/.test(new_password) || !/[0-9]/.test(new_password)) {
-    return res.status(400).json({ error: 'Password must contain at least one uppercase letter, one lowercase letter, and one number' });
-  }
+  const pwCheck = validatePassword(new_password);
+  if (!pwCheck.ok) return res.status(400).json({ error: pwCheck.reason });
 
   const user = db.prepare('SELECT password_hash FROM users WHERE id = ?').get(authReq.user.id) as { password_hash: string } | undefined;
   if (!user || !bcrypt.compareSync(current_password, user.password_hash)) {