Add register-by-signature, web fixes, bin scripts, docs

- Register by signing service key: GET /v1/service-key, POST /v1/auth/register-by-signature
- Login auto-attempts register first for new users
- Web: default API URL momswap.produktor.duckdns.org, /libs/ static handler
- Docker: webbuild stage for geo-api-client, copy web+libs to runtime
- Bin scripts: test.sh, run.sh, up.sh, down.sh
- docs/ed25519-security-use-cases.md: use cases, message formats, examples
- SERVICE_PUBLIC_KEY env (defaults to ADMIN_PUBLIC_KEY)

Made-with: Cursor

README.md

@@ -20,6 +20,12 @@ go test ./...
 go run ./cmd/api
 ```
 
+Run tests via Docker (avoids local permission issues, e.g. `var/`):
+
+```bash
+docker compose --profile test run --rm test
+```
+
 Primary deployed base URL: `https://momswap.produktor.duckdns.org/`.
 
 Local default (for development): `http://localhost:8122`.
@@ -28,6 +34,7 @@ Optional environment variables:
 
 - `ADDR` (default `:8122`)
 - `ADMIN_PUBLIC_KEY` (bootstrap initial inviter/admin user)
+- `SERVICE_PUBLIC_KEY` (public key users sign to register; defaults to `ADMIN_PUBLIC_KEY`)
 
 ## Docker Compose