Add setup and deployment guide, env example files

- Rewrote README.md with full step-by-step setup guide covering Docker
  Compose deployment, environment configuration, port reference, local
  dev setup, and reset instructions
- Added backend/.env.example and frontend/.env.local.example so new
  deployers know exactly what to configure without any secrets committed
- Updated .gitignore to allow .env.example files through

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/.env.local.example

@@ -0,0 +1,25 @@
+# ─────────────────────────────────────────────────────────────────
+# BMS Frontend — Environment Variables
+# Copy this file to .env.local and fill in your values.
+# Never commit .env.local to git.
+# ─────────────────────────────────────────────────────────────────
+
+# Clerk authentication
+# Get these from https://dashboard.clerk.com → Your App → API Keys
+NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY=pk_test_REPLACE_ME
+CLERK_SECRET_KEY=sk_test_REPLACE_ME
+
+# Clerk redirect paths — no change needed
+NEXT_PUBLIC_CLERK_SIGN_IN_URL=/sign-in
+NEXT_PUBLIC_CLERK_SIGN_UP_URL=/sign-up
+NEXT_PUBLIC_CLERK_AFTER_SIGN_IN_URL=/dashboard
+NEXT_PUBLIC_CLERK_AFTER_SIGN_UP_URL=/dashboard
+
+# API path — leave as-is
+# All /api/backend/* requests are proxied server-side to the FastAPI backend
+NEXT_PUBLIC_API_URL=/api/backend
+
+# Backend internal URL (used by Next.js server-side proxy, not sent to browser)
+# In Docker: http://backend:8000
+# In local dev: http://localhost:8000
+BACKEND_INTERNAL_URL=http://backend:8000