Add account page with name edit and password management

[ICubE01]

Summary

• New /account page: displays name (inline edit) and email; links to password change for password-based accounts
• New /account/change-password page: form to change current password
• NavBar redesigned: user dropdown (계정/로그아웃) and a home link that returns to the current room if in one
• New GET /users/{id} endpoint returns full account profile (AccountDto) including linked identities

Backend

Features

• GET /api/users/{id} — returns AccountDto { user: UserDto, identities: UserIdentityDto[] }
• PATCH /api/users/{id}/password — changes password; throws NoPasswordException (400) for social-only accounts, WrongPasswordException (406) for wrong current password
• UserDto expanded: id, name, email, hasPassword, createdAt
• AccountDto aggregates UserDto + List<UserIdentityDto>

Refactor

• UserController.isNotCurrentUserId helper centralises the ownership guard (was copy-pasted in each handler)
• ConnectedIdentityResponse renamed to UserIdentityDto; SocialAuthController.getConnectedIdentities removed (now served via GET /users/{id})
• DuplicateUserException renamed to DuplicateEmailException
• UserMapper.toDto derives hasPassword from user.getPassword() != null

Frontend

Features

• AccountPage.tsx — shows name (inline edit) and email from GET /users/{id}; links to /account/change-password for password accounts only
• ChangePasswordPage.tsx — form with current/new/confirm password fields; redirects back to /account on success; guards: JS validation for empty current password, backend @NotBlank enforcement
• NavBar.tsx — replaced settings gear with user-name dropdown; "Tichu Sim" home link navigates to current room (/rooms/:roomId) or / depending on route
• types.ts — added UserDto, AccountDto, UserIdentityDto, OidcProviderName