* feat: add tools API endpoint and tools-selector form type
Backend:
- Add GET /api/v1/tools — list all available tools (plugin + MCP)
- Add GET /api/v1/tools/<tool_name> — get specific tool details
Frontend:
- Add TOOLS_SELECTOR form type for plugin config forms
- Multi-select dialog with tool name and description
- Add PluginTool entity type and API client methods
* fix: remove unused quart import, fix prettier formatting
* style: ruff format tools.py
* chore: bump langbot-plugin to 0.3.7
