Implement multi-user auth + agent management + terminal proxy

- Add userId to agents and projects tables (with migrations)
- Create auth middleware for session validation
- Protect MCP endpoints with authentication and user filtering
- Implement agent management API (launch, my, delete)
- Add terminal proxy at /agent-terminal/:agentId with auth
- Update all agent endpoints to verify user ownership

Co-Authored-By: Claude Sonnet 4.5 (1M context) <noreply@anthropic.com>

drizzle/migrations/meta/_journal.json

@@ -15,6 +15,13 @@
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       "breakpoints": true
+    },
+    {
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+      "version": "5",
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+      "tag": "0002_next_xorn",
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   ]
 }