refactor: single-user web-based setup — replace env config with Settings UI

Move from multi-user env-var config to single-user web-first architecture:
- Add SetupPage for first-time initialization (replaces /register)
- Add SettingsPage for AI models, exchanges, Telegram, and password management
- Enrich all API route schemas with exact ID usage documentation
- Add PUT /user/password endpoint for in-app password changes
- Remove REGISTRATION_ENABLED, MAX_USERS, TELEGRAM_BOT_TOKEN from env config
- Simplify LoginPage design, remove admin mode and registration links
- Telegram bot now resolves user email for identity display
- start.sh no longer runs interactive Telegram setup

web/src/components/AITradersPage.tsx

@@ -1499,7 +1499,7 @@ function ModelCard({
 }
 
 // Model Configuration Modal Component
-function ModelConfigModal({
+export function ModelConfigModal({
   allModels,
   configuredModels,
   editingModelId,