feat: initial corvid — standalone ticket service extracted from homelab-dashboard

Extracts the ticket/attachment system into a reusable pip-installable package.
Centralises homelab MCP server (tickets, attachments, system logs) here.

- corvid package: models, router (make_router factory), config, standalone main
- Alembic migration chain for fresh standalone deployments
- Docker Compose for standalone deployment (port 8090)
- mcp_server.py: moved from homelab-dashboard, CORVID_REPO_PATH configurable

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

docker-compose.yml

@@ -0,0 +1,28 @@
+services:
+  postgres:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER:     corvid
+      POSTGRES_PASSWORD: corvid
+      POSTGRES_DB:       corvid
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U corvid"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+
+  app:
+    build: .
+    ports:
+      - "8090:8080"
+    env_file:
+      - .env
+    depends_on:
+      postgres:
+        condition: service_healthy
+    restart: unless-stopped
+
+volumes:
+  pgdata: