feat: Implement comprehensive security hardening

Security Improvements:
- Auto-generate AUTH_SECRET and admin credentials on first launch
  - Cryptographically secure random generation
  - Stored in database for persistence
  - Logged once to container logs for admin retrieval

- Implement CSRF protection with double-submit cookie pattern
  - Three-way validation: cookie, header, and session database
  - Automatic client-side injection via plugin
  - Server middleware for automatic validation
  - Zero frontend code changes required

- Add session fixation prevention with automatic invalidation
  - Regenerate sessions on password changes
  - Keep current session active, invalidate others on profile password change
  - Invalidate ALL sessions on forgot-password reset
  - Invalidate ALL sessions on admin password reset

- Upgrade password reset codes to 8-char alphanumeric
  - Increased from 1M to 1.8 trillion combinations
  - Uses crypto.randomInt() for cryptographic randomness
  - Excluded confusing characters (I, O) for better UX
  - Case-insensitive verification

- Implement dual-layer account lockout
  - IP-based rate limiting (existing)
  - Per-account lockout: 10 attempts = 30 min lock
  - Automatic unlock after expiration
  - Admin manual unlock via UI
  - Visual status indicators in users table

Database Changes:
- Add csrf_token column to sessions table
- Add failed_login_attempts and locked_until columns to users table
- Add settings table for persistent AUTH_SECRET storage
- All migrations backward-compatible with try-catch

New Files:
- server/utils/csrf.ts - CSRF protection utilities
- server/middleware/csrf.ts - Automatic CSRF validation middleware
- plugins/csrf.client.ts - Automatic CSRF header injection
- server/api/users/unlock/[id].post.ts - Admin unlock endpoint

Modified Files:
- server/utils/database.ts - Core security functions and schema updates
- server/utils/email.ts - Enhanced reset code generation
- server/api/auth/login.post.ts - CSRF + account lockout logic
- server/api/auth/register.post.ts - CSRF token generation
- server/api/auth/logout.post.ts - CSRF cookie cleanup
- server/api/auth/reset-password.post.ts - Session invalidation
- server/api/auth/verify-reset-code.post.ts - Case-insensitive codes
- server/api/profile/update.put.ts - Session invalidation on password change
- server/api/users/password/[id].put.ts - Session invalidation on admin reset
- pages/users.vue - Lock status display and unlock functionality
- docker-compose.yml - Removed default credentials
- nuxt.config.ts - Support auto-generation

All changes follow OWASP best practices and are production-ready.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

server/api/auth/register.post.ts

@@ -1,5 +1,6 @@
 import { createUser, getUserByUsername, getUserByEmail, checkRateLimit, createSession } from '~/server/utils/database'
 import { setAuthCookie, generateSessionToken } from '~/server/utils/auth'
+import { generateCsrfToken, setCsrfCookie } from '~/server/utils/csrf'
 
 export default defineEventHandler(async (event) => {
   // Get real client IP from proxy headers (prioritize x-real-ip for NPM)
@@ -107,15 +108,21 @@ export default defineEventHandler(async (event) => {
   try {
     // Create the new user with all fields
     createUser(username.toLowerCase(), password, email.toLowerCase(), firstName, lastName)
-    
-    // Generate session token and create session for auto-login
+
+    // Generate session token and CSRF token for auto-login
     const sessionToken = generateSessionToken()
+    const csrfToken = generateCsrfToken()
     const expiresAt = new Date(Date.now() + 24 * 60 * 60 * 1000).toISOString() // 24 hours
-    createSession(sessionToken, username.toLowerCase(), expiresAt)
-    
+
+    // Create session with CSRF token
+    createSession(sessionToken, username.toLowerCase(), expiresAt, csrfToken)
+
     // Set session cookie
     setAuthCookie(event, sessionToken)
-    
+
+    // Set CSRF cookie
+    setCsrfCookie(event, csrfToken)
+
     // Log successful registration
     console.log(`[REGISTER SUCCESS] User: ${username.toLowerCase()}, IP: ${clientIp}`)