Add static API-key auth, dockerize service, publish façade docs

- sms/auth.py: verify_api_key dependency (Bearer/X-API-Key, SHA-256 hash
  compare via secrets.compare_digest, fail-closed 503 if no hash). All routes
  gated via a protected router; /health stays open for probes.
- config.py: new sms_api_key_hash setting (VOIPMS_SMS_API_KEY_HASH).
- Dockerfile + .dockerignore + docker-compose.yml: lean python:3.13-slim
  image; secrets injected via env_file, never baked in; host-localhost-only
  port mapping (SMS_PORT override); /health healthcheck.
- .env.example: committed template (placeholders only, no secrets).
- sms/docs/sms-facade.dokuwiki.txt: abstraction API reference (published to
  the apidoc wiki at voipms:sms-facade).
- README: Authentication section, Docker section, 401/503 error rows.

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

docker-compose.yml

@@ -0,0 +1,22 @@
+# voip.ms SMS/MMS API façade.
+# Secrets live in the host .env (gitignored) and are injected here via env_file;
+# they are never baked into the image.
+services:
+  sms:
+    build: .
+    image: sms-api-wrapper:latest
+    container_name: sms-api
+    # Host-localhost only. To expose on the LAN, change to "8000:8000"
+    # (access is still gated by the VOIPMS_SMS_API_KEY_HASH API key).
+    # Override the host port with SMS_PORT (e.g. SMS_PORT=8001 in .env) if 8000 is taken.
+    ports:
+      - "127.0.0.1:${SMS_PORT:-8000}:8000"
+    env_file:
+      - .env
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://127.0.0.1:8000/health').read()"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 10s