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/domain/repository/image_cache.rs

@@ -0,0 +1,19 @@
+//! Repository trait for image cache (original → CDN mapping).
+
+use async_trait::async_trait;
+
+/// Repository for managing cached image URL mappings.
+#[async_trait]
+pub trait ImageCacheRepository: Send + Sync {
+    async fn get_from_redis(&self, key: &str) -> Option<String>;
+    async fn set_in_redis(&self, key: &str, value: &str, ttl: u64) -> Result<(), String>;
+    async fn get_from_db(&self, original_url: &str) -> Result<Option<String>, String>;
+    async fn save_to_db(&self, original_url: &str, cdn_url: &str) -> Result<(), String>;
+    async fn find_original_from_cdn(&self, cdn_url: &str) -> Result<Option<String>, String>;
+    async fn delete_from_db(&self, original_url: &str) -> Result<(), String>;
+    async fn delete_from_redis(&self, key: &str) -> Result<(), String>;
+    async fn get_lock(&self, key: &str) -> bool;
+    async fn set_lock(&self, key: &str, ttl: u64) -> Result<(), String>;
+    async fn release_lock(&self, key: &str) -> Result<(), String>;
+    async fn invalidate_api_caches(&self, patterns: Vec<&str>) -> Result<(), String>;
+}

src/domain/repository/mod.rs

@@ -0,0 +1,5 @@
+pub mod image_cache;
+pub mod scraping;
+
+pub use image_cache::ImageCacheRepository;
+pub use scraping::ScrapingRepository;

src/domain/repository/scraping.rs

@@ -0,0 +1,12 @@
+//! Repository trait for scraping HTML from remote sources.
+
+use async_trait::async_trait;
+
+use crate::domain::error::ScrapingError;
+
+/// Trait for repositories that fetch and scrape HTML content.
+#[async_trait]
+pub trait ScrapingRepository: Send + Sync {
+    /// Fetch raw HTML from a URL.
+    async fn fetch_html(&self, url: &str) -> Result<String, ScrapingError>;
+}