chore: add prod deploy files — migration service + env example

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

.env.prod.example

@@ -0,0 +1,26 @@
+# Tessera Production Environment
+# Copy to .env and fill in all values before running docker compose up
+
+# Database
+DB_PASSWORD=change-me-strong-password
+DATABASE_URL=postgresql://tessera:change-me-strong-password@db:5432/tessera
+
+# App
+APP_URL=https://tessera.deine-domain.de
+JWT_SECRET=change-me-64-char-random-string
+
+# Admin account (created on first start)
+TESSERA_ADMIN_USER=admin
+TESSERA_ADMIN_EMAIL=admin@deine-domain.de
+TESSERA_ADMIN_PASSWORD=change-me-strong-password
+
+# Calendar encryption key — generate with: openssl rand -hex 32
+CALENDAR_ENCRYPTION_KEY=
+
+# SMTP (optional)
+TESSERA_SMTP_HOST=
+TESSERA_SMTP_PORT=587
+TESSERA_SMTP_SECURE=false
+TESSERA_SMTP_USER=
+TESSERA_SMTP_PASSWORD=
+TESSERA_SMTP_FROM=Tessera <noreply@deine-domain.de>