Add MCP automation interface for quiz round creation (#9)

Add a Quizzical Beats MCP server and automation service for agentic quiz workflows.

Includes tools for catalog lookup/add/import, round creation and naming, MP3/PDF generation and inspection, email delivery, TTS snippet updates, docs, and focused tests.

Deployment intentionally not performed.

docs/developer-guide/mcp.md

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+# MCP Interface
+
+Quizzical Beats includes an MCP server for agentic round production workflows.
+It exposes the same catalog, round, export, email, and custom-audio capabilities
+used by the Flask application.
+
+## Run Locally
+
+Install dependencies and start the MCP server from the repository root:
+
+```bash
+pip install -r requirements.txt
+python -m musicround.mcp_server
+```
+
+The server uses the normal Quizzical Beats Flask configuration. Set the same
+environment variables you use for the web app, including `SECRET_KEY`,
+`AUTOMATION_TOKEN`, database configuration, mail settings, and any Spotify,
+Deezer, OpenAI, AWS Polly, or ElevenLabs credentials needed by the tools you
+plan to call.
+
+## Tools
+
+The MCP server exposes these tools:
+
+| Tool | Purpose |
+| --- | --- |
+| `find_songs` | Search the existing Quizzical Beats catalog before adding duplicates. |
+| `add_song` | Add or update a catalog song, including platform IDs and tags. |
+| `import_catalog_item` | Import a Spotify or Deezer track, album, or playlist. |
+| `compile_round` | Create a named round from explicit song IDs or selection criteria. |
+| `rename_round` | Set or clear a round name. |
+| `create_round_from_playlist` | Import a playlist and turn the imported songs into a round. |
+| `generate_round_assets` | Generate the round PDF and/or MP3. |
+| `inspect_round_mp3` | Check round MP3 duration, loudness, silence, and clipping indicators. |
+| `inspect_round_pdf` | Check round PDF existence and basic structural validity. |
+| `send_round_email` | Generate assets and email the finished round bundle. |
+| `generate_tts_snippet` | Generate and assign custom intro, replay, or outro TTS MP3s. |
+
+## Intended Workflow
+
+1. Search with `find_songs` to avoid duplicates.
+2. Add missing tracks with `add_song` or import platform content with
+   `import_catalog_item`.
+3. Create the round with `compile_round` or `create_round_from_playlist`.
+4. Generate PDF and MP3 files with `generate_round_assets`.
+5. Inspect the generated files with `inspect_round_pdf` and `inspect_round_mp3`.
+6. Send the completed bundle with `send_round_email`.
+
+For Spotify imports, pass a `user_id` for a user with connected Spotify tokens.
+For email, either pass an explicit recipient or use a selected user that has an
+email address.
+
+## Custom Audio
+
+Use `generate_tts_snippet` to update the reusable audio segments:
+
+- `intro`: lead-in before the first song.
+- `replay`: announcement before the repeat section.
+- `outro`: lead-out after the round.
+
+Supported TTS services follow the existing application helper: `openai`, `polly`,
+and `elevenlabs`.