Add infrastructure: Terraform, Docker Compose, BRouter, CD pipeline (#2)

Terraform:
- Hetzner CX22 server with Docker, firewall (80/443/22)
- SSH key and output for server IP

Docker Compose:
- Caddy reverse proxy (auto HTTPS)
- Journal and Planner app containers
- BRouter routing engine container
- PostgreSQL + PostGIS
- Garage S3 storage

BRouter:
- Dockerfile based on eclipse-temurin:11-jre
- Segment download script for Germany (4 tiles, ~750MB)

CD Pipeline:
- Build & push Docker images to ghcr.io on main push
- Deploy step commented out (enable when server provisioned)

Scripts:
- PostgreSQL daily backup with 14-day retention
- Dockerfiles for both apps (multi-stage builds)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

infrastructure/.env.example

@@ -0,0 +1,8 @@
+# trails.cool infrastructure environment variables
+# Copy to .env and fill in values
+
+DOMAIN=trails.cool
+POSTGRES_PASSWORD=change-me
+JWT_SECRET=change-me
+S3_ACCESS_KEY=
+S3_SECRET_KEY=