#2 docs: add documentation site with GitHub Pages deployment

[Anonymous]

Originally created by: grynn-in

Summary

• Adds MkDocs Material site config with dark/light toggle, mermaid diagram support, and full navigation tree for all 32 doc files
• Adds GitHub Actions workflow that auto-deploys to GitHub Pages on push to main
• Includes comprehensive documentation suite: getting started, user guide, API reference, data dictionary, admin/developer guides, troubleshooting, and evaluation docs
• Fixes fiscal calendar fan-out bug and adds P&L/BS/CF Excel workbook

Test plan

• [x] mkdocs build succeeds locally with no missing nav entries
• [x] All 32 doc files resolve in the nav tree
• [ ] After merge, verify GitHub Pages deploys at https://grynn-in.github.io/konsolidat/

🤖 Generated with Claude Code

[Anonymous]

Ticket changed by: grynn-in

• status: open --> closed