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

store/user.go

@@ -97,6 +97,13 @@ func (s *UserStore) GetAllIDs() ([]string, error) {
 	return userIDs, err
 }
 
+// GetAll returns all users ordered by creation time.
+func (s *UserStore) GetAll() ([]User, error) {
+	var users []User
+	err := s.db.Model(&User{}).Order("created_at").Find(&users).Error
+	return users, err
+}
+
 // UpdatePassword updates password
 func (s *UserStore) UpdatePassword(userID, passwordHash string) error {
 	return s.db.Model(&User{}).Where("id = ?", userID).Updates(map[string]interface{}{