docs: align all documentation to actual env variable names used in code (IN_*, IG_*, OPENAI_*)

[xingzihai]

Summary

This PR aligns all documentation to match the actual environment variable names used in the code.

Changes

1. src/local.settings.json.example

   • Updated to use IN_ACCESS_TOKEN, IN_OWNER, IG_ACCESS_TOKEN, IG_ACCOUNT_ID, OPENAI_API_KEY
   • Removed deprecated variables: LINKEDIN_CLIENT_ID, LINKEDIN_CLIENT_SECRET, KEYVAULT_URI, AZURE_OPENAI_ENDPOINT, AZURE_OPENAI_KEY, AZURE_OPENAI_DEPLOYMENT_NAME

2. docs/configuration.md

   • Updated LinkedIn section with new variable names (IN_ACCESS_TOKEN, IN_OWNER)
   • Updated Instagram section with new variable names (IG_ACCESS_TOKEN, IG_ACCOUNT_ID)
   • Updated AI section to use OPENAI_API_KEY
   • Added "Future / Planned" section for deprecated variables

3. README.md

   • Updated Configuration → Local Development JSON example
   • Updated Multi-Platform Publishing → LinkedIn description
   • Updated Multi-Platform Publishing → Instagram description with production readiness link

4. ARCHITECTURE.md

   • Updated ADR-004 to reflect OpenAI direct API usage
   • Updated models: gpt-4.1-nano for summarisation, gpt-image-1.5 for image generation

Testing

This is a documentation-only change. No production code modifications.

Fixes #70

[artcava]

Hi @xingzihai! 👋

Thank you so much for this contribution — the documentation alignment is very well done and really improves the clarity of the project for everyone.

Just one note for future contributions: even for documentation-only changes, I'd prefer that all PRs branch off from develop rather than directly targeting master. This keeps our branching strategy consistent and makes integration smoother regardless of the type of change.

That said, this is very much appreciated and the work is solid. I'm looking forward to continuing to collaborate with you on this project! 🚀

[artcava]

Documentation changes are accurate and well-structured. Approving and merging. Please note that future PRs should branch off from develop, even for docs-only changes.