feat: Simplify AutoStart and fix critical security vulnerability

Major architectural improvements:
- Remove complex plaintext cache system, use direct database fields
- Replace IP-based authentication with secure token-based auth
- Integrate INTERNAL_AUTH_TOKEN with unified auto-generation system

Security fixes:
- Fix Docker nginx proxy authentication bypass vulnerability in /ssh/db/host/internal
- Replace req.ip detection with X-Internal-Auth-Token header validation
- Add production environment security checks for internal auth token

AutoStart simplification:
- Add autostart_{password,key,key_password} columns directly to ssh_data table
- Remove redundant autostartPlaintextCache table and AutoStartPlaintextManager
- Implement enable/disable/status endpoints for autostart management
- Update frontend to handle autostart cache lifecycle automatically

Environment variable improvements:
- Integrate INTERNAL_AUTH_TOKEN into SystemCrypto auto-generation
- Unified .env file management for all security keys (JWT, Database, Internal Auth)
- Auto-generate secure tokens with proper entropy (256-bit)

API improvements:
- Make /users/oidc-config and /users/registration-allowed public for login page
- Add /users/setup-required endpoint replacing problematic getUserCount usage
- Restrict /users/count to admin-only access for security

Database schema:
- Add autostart plaintext columns to ssh_data table with proper migrations
- Remove complex cache table structure for simplified data model

src/backend/database/db/index.ts

@@ -299,6 +299,7 @@ async function initializeCompleteDatabase(): Promise<void> {
         FOREIGN KEY (host_id) REFERENCES ssh_data (id),
         FOREIGN KEY (user_id) REFERENCES users (id)
     );
+
 `);
 
   // Run schema migrations
@@ -435,6 +436,11 @@ const migrateSchema = () => {
     "INTEGER REFERENCES ssh_credentials(id)",
   );
 
+  // AutoStart plaintext columns
+  addColumnIfNotExists("ssh_data", "autostart_password", "TEXT");
+  addColumnIfNotExists("ssh_data", "autostart_key", "TEXT");
+  addColumnIfNotExists("ssh_data", "autostart_key_password", "TEXT");
+
 
   // SSH credentials table migrations for encryption support
   addColumnIfNotExists("ssh_credentials", "private_key", "TEXT");