Add comprehensive n8n integration documentation with 5-step workflow tutorial

[devin-ai-integration]

Add comprehensive n8n integration documentation with 5-step workflow tutorial

Summary

Added complete n8n integration documentation to AssemblyAI docs with a comprehensive 5-step workflow tutorial covering:

1. Upload audio file (local/remote/Google Drive options)
2. Submit transcription with available features (speaker labels, language detection, etc.)
3. Poll for completion with loop and status checking
4. Process transcript output (format, save to Google Sheets, email, Slack)
5. Retrieve additional data (redacted audio, sentences, paragraphs) and delete transcript

Also includes:

• Webhook alternative to polling
• Error handling section
• Example workflow JSON for import (simplified version)
• Code examples for formatting transcripts (JavaScript and Python)
• Popular integration pairings and use cases

Additional fixes:

• Fixed pre-existing CSS syntax errors in custom-styles.css (missing closing parentheses)
• Added n8n to docs navigation and integrations index page

Review & Testing Checklist for Human

⚠️ Important: This tutorial was created based on API documentation and n8n patterns but was NOT tested in actual n8n. Please verify:

• Test the n8n workflow steps - Follow the tutorial in actual n8n to verify node configurations are correct and the workflow runs successfully
• Verify n8n expression syntax - Check that expressions like {{$node['HTTP Request'].json['upload_url']}} use correct n8n syntax
• Test the example workflow JSON - Import the JSON into n8n to ensure it's valid (note: it's simplified and missing polling loop/error handling)
• Check docs navigation - Verify the n8n page appears at /docs/integrations/n-8-n and is accessible from the integrations section
• Review CI failures - Confirm the lint/fern-check failures are pre-existing issues (my commit only touched n8n.mdx, custom-styles.css, docs.yml, and index.mdx)

Test Plan

1. Navigate to /docs/integrations/n-8-n in the docs
2. Follow the tutorial steps in n8n Cloud or self-hosted instance
3. Try importing the example workflow JSON
4. Verify all links and code examples render correctly

Notes

• CI Status: Lint and fern-check are failing with pre-existing OpenAPI spec issues (word_boost/boost_param properties, missing Authorization headers). These errors existed before my changes and affect other recent PRs.
• Screenshots: Griffin will add UI screenshots later - this PR provides the text-based tutorial foundation
• Workflow JSON: The example JSON is labeled as "simplified" and doesn't include the full polling loop/error handling. Consider whether this should be expanded to a fully working example.
• CSS Fix: Fixed missing closing parentheses in custom-styles.css that were causing lint failures

Requested by: Griffin (after initial request from Ryan Seams - rseams@assemblyai.com, @ryanseams)
Devin session: https://app.devin.ai/sessions/a6048fb84ba64a47b9f68f801ed719db

[devin-ai-integration]

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