refactor: restructure application to CQRS, update api-types + presentation

- application: replace flat use_cases/ with identity/{commands,queries}/ and organization/commands/
- each use case now split into Command/Query struct + Handler struct
- api-types: add username to RegisterRequest/UserResponse, add CreateAlbumRequest/AlbumResponse
- presentation: update state, handlers, factory to use new handler types
- tests: restructured to match CQRS module layout, added get_profile tests

crates/presentation/src/handlers/auth.rs

@@ -3,6 +3,7 @@ use api_types::{
     requests::{LoginRequest, RegisterRequest},
     responses::{AuthResponse, UserResponse},
 };
+use application::identity::{RegisterUserCommand, LoginUserCommand, GetProfileQuery};
 use crate::{errors::AppError, extractors::{JwtClaims, ValidatedJson}, state::AppState};
 
 #[utoipa::path(
@@ -18,7 +19,12 @@ pub async fn register(
     State(state): State<AppState>,
     ValidatedJson(req): ValidatedJson<RegisterRequest>,
 ) -> Result<(StatusCode, Json<AuthResponse>), AppError> {
-    let user = state.register_uc.execute(&req.email, &req.password).await?;
+    let cmd = RegisterUserCommand {
+        username: req.username,
+        email: req.email,
+        password: req.password,
+    };
+    let user = state.register_handler.execute(cmd).await?;
     let token = state.token_issuer.issue(&user.id, "user").await.map_err(AppError::from)?;
     Ok((StatusCode::CREATED, Json(AuthResponse { token, user: UserResponse::from_domain(&user) })))
 }
@@ -35,7 +41,11 @@ pub async fn login(
     State(state): State<AppState>,
     ValidatedJson(req): ValidatedJson<LoginRequest>,
 ) -> Result<Json<AuthResponse>, AppError> {
-    let (user, token) = state.login_uc.execute(&req.email, &req.password).await?;
+    let cmd = LoginUserCommand {
+        email: req.email,
+        password: req.password,
+    };
+    let (user, token) = state.login_handler.execute(cmd).await?;
     Ok(Json(AuthResponse { token, user: UserResponse::from_domain(&user) }))
 }
 
@@ -51,6 +61,7 @@ pub async fn me(
     State(state): State<AppState>,
     claims: JwtClaims,
 ) -> Result<Json<UserResponse>, AppError> {
-    let user = state.get_profile_uc.execute(&claims.user_id).await?;
+    let query = GetProfileQuery { user_id: claims.user_id };
+    let user = state.get_profile_handler.execute(query).await?;
     Ok(Json(UserResponse::from_domain(&user)))
 }