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>

alembic/env.py

@@ -0,0 +1,33 @@
+import asyncio
+from logging.config import fileConfig
+
+from sqlalchemy.ext.asyncio import create_async_engine
+
+from alembic import context
+
+alembic_cfg = context.config
+
+if alembic_cfg.config_file_name is not None:
+    fileConfig(alembic_cfg.config_file_name)
+
+from corvid import config as app_config
+from corvid.models import Base  # noqa: E402 — registers models
+
+target_metadata = Base.metadata
+
+
+def do_run_migrations(connection):
+    context.configure(connection=connection, target_metadata=target_metadata)
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+async def run_async_migrations():
+    engine = create_async_engine(app_config.DATABASE_URL)
+    async with engine.begin() as conn:
+        await conn.run_sync(do_run_migrations)
+    await engine.dispose()
+
+
+run_migrations_online = lambda: asyncio.run(run_async_migrations())
+run_migrations_online()