Drop DATABASE_URL/MASTER_KEY_PATH from .env.example

docker-compose.yml already overrides both to point at the bind-mounted
./data/ dirs, and app/config.py has sensible hardcoded defaults for
local (non-Docker) dev, so neither needs to live in .env.

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

.env.example

@@ -1,5 +1,3 @@
-DATABASE_URL=sqlite+aiosqlite:///./plm_lottery.db
-
 ELECTRUM_HOST=santantonio.sytes.net
 ELECTRUM_PORT=50002
 ELECTRUM_USE_SSL=true
@@ -7,7 +5,6 @@ ELECTRUM_USE_SSL=true
 # Fernet key protecting the master xprv at rest. Generate with:
 #   python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
 XPRV_ENCRYPTION_KEY=
-MASTER_KEY_PATH=./master.xprv.enc
 
 # Random secret for JWT session signing. Generate with:
 #   python -c "import secrets; print(secrets.token_urlsafe(32))"