Update to use MySQL Database

CLAUDE.md

@@ -23,6 +23,7 @@ For a single Go package test: `go test ./internal/volunteer/...`
 ## Architecture
 
 ### Go Backend
+
 Domain-based packaging under `internal/` — each domain owns its models, store (DB queries), and HTTP handler in a single package:
 
 | Package | Responsibility |
@@ -43,23 +44,31 @@ Domain-based packaging under `internal/` — each domain owns its models, store
 All API routes are prefixed `/api/v1`. The Go binary serves the compiled React app from `STATIC_DIR` (default `./web/dist`) for all non-API routes.
 
 ### React Frontend
+
 Standard CRA layout in `web/src/`:
+
 - `api.ts` — typed fetch wrapper; reads JWT from `localStorage`, prefixes `BASE = '/api/v1'`
 - `auth.tsx` — `AuthProvider` context; decodes the JWT payload to expose `role` and `volunteerID`
 - `pages/` — one file per route (`Dashboard`, `Schedules`, `TimeOff`, `Volunteers`, `Login`)
 - `App.tsx` — `BrowserRouter` with a `ProtectedLayout` that redirects to `/login` when no token is present; admin-only nav links gated on `role === 'admin'`
 
 ### Data Storage
-SQLite via `modernc.org/sqlite` (pure Go, no CGO). Schema is defined inline in `internal/db/schema.go` and applied via `CREATE TABLE IF NOT EXISTS` on every startup. No migration framework — additive changes are safe; destructive changes require manual handling.
+
+MySQL 8.0 via `github.com/go-sql-driver/mysql`. Schema is defined inline in `internal/db/schema.go` and applied via `CREATE TABLE IF NOT EXISTS` on every startup. No migration framework — additive changes are safe; destructive changes require manual handling.
 
 ### Auth
+
 HS256 JWT signed with `JWT_SECRET`. Token payload: `{ volunteer_id, role, exp }`. Role is either `volunteer` or `admin`. The `RequireAdmin` middleware enforces admin-only routes server-side.
 
 ## Environment Variables
 
 | Variable | Default | Description |
 |----------|---------|-------------|
-| `DATABASE_DSN` | `walkies.db` | SQLite file path |
+| `DB_HOST` | `localhost` | MySQL host |
+| `DB_PORT` | `3306` | MySQL port |
+| `DB_USER` | `root` | MySQL username |
+| `DB_PASSWORD` | `` | MySQL password |
+| `DB_NAME` | `walkies` | MySQL database name |
 | `JWT_SECRET` | `change-me-in-production` | HMAC signing key |
 | `STATIC_DIR` | `./web/dist` | Path to compiled React app |
 | `PORT` | `8080` | HTTP listen port |