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>

Cargo.lock

@@ -3347,7 +3347,6 @@ dependencies = [
  "itertools",
  "log",
  "mime_guess",
- "once_cell",
  "opentelemetry",
  "opentelemetry-otlp",
  "opentelemetry-semantic-conventions",