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>

docker-compose.yml

@@ -0,0 +1,42 @@
+services:
+  postgres:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER: ${POSTGRES_USER:-mangalord}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-mangalord}
+      POSTGRES_DB: ${POSTGRES_DB:-mangalord}
+    volumes:
+      - postgres-data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-mangalord}"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+
+  backend:
+    build: ./backend
+    depends_on:
+      postgres:
+        condition: service_healthy
+    environment:
+      DATABASE_URL: postgres://${POSTGRES_USER:-mangalord}:${POSTGRES_PASSWORD:-mangalord}@postgres:5432/${POSTGRES_DB:-mangalord}
+      BIND_ADDRESS: 0.0.0.0:8080
+      STORAGE_DIR: /var/lib/mangalord/storage
+      RUST_LOG: ${RUST_LOG:-info,mangalord=debug}
+    volumes:
+      - storage-data:/var/lib/mangalord/storage
+    ports:
+      - "8080:8080"
+
+  frontend:
+    build: ./frontend
+    depends_on:
+      - backend
+    environment:
+      PUBLIC_API_BASE: ${PUBLIC_API_BASE:-http://localhost:8080/api}
+    ports:
+      - "3000:3000"
+
+volumes:
+  postgres-data:
+  storage-data: