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/config.rs

@@ -0,0 +1,22 @@
+use std::path::PathBuf;
+
+#[derive(Clone, Debug)]
+pub struct Config {
+    pub database_url: String,
+    pub bind_address: String,
+    pub storage_dir: PathBuf,
+}
+
+impl Config {
+    pub fn from_env() -> anyhow::Result<Self> {
+        Ok(Self {
+            database_url: std::env::var("DATABASE_URL")
+                .map_err(|_| anyhow::anyhow!("DATABASE_URL must be set"))?,
+            bind_address: std::env::var("BIND_ADDRESS")
+                .unwrap_or_else(|_| "0.0.0.0:8080".to_string()),
+            storage_dir: std::env::var("STORAGE_DIR")
+                .unwrap_or_else(|_| "./data/storage".to_string())
+                .into(),
+        })
+    }
+}