feat: full clean architecture refactor — domain → application → infrastructure → presentation

- Restructure from Modular MVC to Clean Architecture with 4 strict layers
- Domain: entities (anime/komik/proxy), Repository traits, typed errors
- Application: use case classes with proper error propagation
- Infrastructure: repository impls, parsers, Redis cache, HTTP/scraping, browser
- Presentation: Axum handlers, DTOs, AppState, router, AppError+IntoResponse
- Migrate all parsers (otakudesu, alqanime, komik) to native infra implementations
- Replace once_cell::sync::Lazy/OnceCell with std::sync::LazyLock/OnceLock
- Remove 150+ old files in modules/ and shared/ directories
- Remove once_cell from Cargo.toml dependencies
- Fix test/debug binaries to use new import paths
- Zero new clippy warnings

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/presentation/state.rs

@@ -0,0 +1,28 @@
+//! Application state shared across all handlers.
+
+use std::sync::Arc;
+
+use deadpool_redis::Pool;
+use sea_orm::DatabaseConnection;
+
+use crate::events::bus::EventBus;
+use crate::infrastructure::repository::SeaOrmImageCacheRepository;
+
+/// Shared application state injected into every handler via Axum State.
+///
+/// Contains the infrastructure dependencies that handlers and use cases
+/// need to serve requests.
+#[derive(Clone)]
+pub struct AppState {
+    pub redis_pool: Pool,
+    pub db: Arc<DatabaseConnection>,
+    pub image_processing_semaphore: Arc<tokio::sync::Semaphore>,
+    pub event_bus: Arc<EventBus>,
+    pub image_cache_repo: Arc<SeaOrmImageCacheRepository>,
+}
+
+impl AppState {
+    pub fn sea_orm(&self) -> &DatabaseConnection {
+        &self.db
+    }
+}