chore: initial project scaffold

Set up Mangalord with a Rust/axum backend, SvelteKit frontend, Postgres,
and Docker Compose deployment. Establishes the architecture and TDD
patterns the project will extend:

- Hexagonal-ish backend layering (domain / repo / storage / api) with
  a pluggable Storage trait (LocalStorage today, S3 as a future impl).
- Initial migration: users, mangas, chapters, bookmarks.
- Vertical slice for mangas (list, search, create, get) with
  #[sqlx::test] integration coverage and storage unit tests.
- SvelteKit frontend using Svelte 5 runes, typed API client, Vitest
  unit tests and Playwright e2e with route mocking.
- CLAUDE.md documenting layering, TDD/git/SemVer workflow rules, and
  extension points (tags, fulltext search, OCR, S3, auth).
- Project-scoped .claude/settings.json with permission allowlist for
  the toolchain (git, cargo, npm/vite, docker, psql, gh, doc fetches).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/src/api/files.rs

@@ -0,0 +1,39 @@
+//! Serves blobs from the `Storage` trait. Same endpoint serves manga
+//! covers and chapter pages; the key embedded in the URL is whatever
+//! the writer stored.
+
+use axum::extract::{Path, State};
+use axum::http::header;
+use axum::response::{IntoResponse, Response};
+use axum::routing::get;
+use axum::Router;
+
+use crate::app::AppState;
+use crate::error::AppResult;
+use crate::storage::StorageError;
+
+pub fn routes() -> Router<AppState> {
+    Router::new().route("/files/*key", get(serve))
+}
+
+async fn serve(State(state): State<AppState>, Path(key): Path<String>) -> AppResult<Response> {
+    let bytes = match state.storage.get(&key).await {
+        Ok(b) => b,
+        Err(StorageError::NotFound) => return Err(crate::error::AppError::NotFound),
+        Err(e) => return Err(e.into()),
+    };
+    let ct = content_type_for(&key);
+    Ok(([(header::CONTENT_TYPE, ct)], bytes).into_response())
+}
+
+fn content_type_for(key: &str) -> &'static str {
+    let ext = key.rsplit('.').next().unwrap_or("").to_ascii_lowercase();
+    match ext.as_str() {
+        "jpg" | "jpeg" => "image/jpeg",
+        "png" => "image/png",
+        "webp" => "image/webp",
+        "gif" => "image/gif",
+        "avif" => "image/avif",
+        _ => "application/octet-stream",
+    }
+}