Add Docker Compose setup for local runs

PHP 8.3 + Apache image serving public/ on port 8080, with pdo_sqlite and
mbstring built in. The container entrypoint applies migrations as www-data
before starting Apache; the SQLite database and generated JWT signing key
persist in a named "storage" volume. `docker compose up -d` is now the
primary way to run the project without a local PHP toolchain.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -11,18 +11,35 @@ SQLite file, plus a single-page frontend (added in a later stage).
 | 2 | Todo CRUD API | planned |
 | 3 | Single-page frontend | planned |
 
-## Requirements
+## Run with Docker
 
-- PHP 8.1+ with the `pdo_sqlite` and `mbstring` extensions
-- [Composer](https://getcomposer.org/)
+The only requirement is Docker with the Compose plugin.
 
-On Fedora:
+```bash
+docker compose up -d
+```
+
+This builds a PHP 8.3 + Apache image, applies migrations, and serves the API at
+<http://localhost:8080> (e.g. `curl http://localhost:8080/api/health`).
+
+- The SQLite database and the generated JWT signing key live in the `storage`
+  named volume, so they survive `docker compose restart` / `down` + `up`.
+- After changing PHP source or `composer.json`, rebuild: `docker compose up -d --build`.
+- `docker compose down -v` removes the volume and gives you a clean database.
+- Override settings via the environment or a `.env` file in this directory
+  (Compose substitutes `APP_DEBUG`, `JWT_SECRET`, `JWT_TTL` — see
+  [docker-compose.yml](docker-compose.yml)).
+
+## Run without Docker
+
+Requires PHP 8.1+ with the `pdo_sqlite` and `mbstring` extensions, plus
+[Composer](https://getcomposer.org/). On Fedora:
 
 ```bash
 sudo dnf install php-cli php-pdo php-mbstring composer
 ```
 
-## Setup
+### Setup
 
 ```bash
 composer install
@@ -30,7 +47,7 @@ cp .env.example .env      # optional; sane defaults are used without it
 composer migrate          # creates storage/database.sqlite and its tables
 ```
 
-## Running
+### Running
 
 ```bash
 composer serve            # http://localhost:8080  (php -S localhost:8080 -t public)
@@ -154,6 +171,9 @@ src/Http/JsonErrorHandler.php Uniform JSON error envelope
 src/Http/Controllers/        Request handlers
 src/Repository/              Database access
 migrations/*.sql             Schema, applied by bin/migrate.php
+Dockerfile                   PHP 8.3 + Apache image
+docker-compose.yml           One-command local stack
+docker/                      Apache vhost + container entrypoint
 ```
 
 ## Provenance