Initialize FastAPI migration with modern Python structure

This commit establishes the foundation for migrating Imbi from Tornado
to FastAPI with AI integration capabilities.

Changes:
- Add pyproject.toml with modern Python packaging (Hatchling)
- Create src/imbi/ directory structure for consolidated codebase
- Add comprehensive PRD documenting FastAPI migration and Claude/MCP integration
- Add MIGRATION.md guide for administrators and developers
- Update .gitignore for modern Python development

Key architectural decisions:
- Python 3.12+ exclusively
- FastAPI for async web framework
- Piccolo ORM for type-safe database operations
- Anthropic Claude SDK for conversational AI
- Model Context Protocol (MCP) for external AI integration

New features planned:
- Claude-powered chat interface for natural language queries
- MCP server for Claude Desktop and IDE integration
- Auto-generated OpenAPI specification
- Consolidated repository (eliminate openapi/ and ddl/ submodules)

Repository consolidation:
- Move api/ submodule code to src/imbi/
- Replace DDL migrations with Piccolo migrations
- Remove openapi/ submodule (FastAPI auto-generates)
- Remove all GitLab integration code

🤖 Generated with Claude Code

Author: gmr

.gitignore

@@ -1,20 +1,102 @@
-__pycache__
-.bak
-*.egg-info
+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
 *.pyc
-*.env
-env/
+*.egg-info
+.Python
 build/
-ddl/build/
+develop-eggs/
 dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+MANIFEST
+
+# Virtual environments
+env/
+.venv/
+venv/
+ENV/
+
+# Testing
+.pytest_cache/
+.coverage
+.coverage.*
+htmlcov/
+.tox/
+.nox/
+coverage.xml
+*.cover
+
+# IDEs
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+.DS_Store
+.bak
+
+# Environment files
+*.env
+.env
+.env.local
+.env.*.local
+
+# Logs
+*.log
+logs/
+
+# Database
+*.db
+*.sqlite
+*.sqlite3
 ddl.sql
+scaffolding/postgres/metadata.sql
+
+# Old structure (will be removed)
+ddl/build/
 imbi/static/fonts/
 imbi/static/*.js
 imbi/static/*.js.map
 openapi/node_modules/
-scaffolding/postgres/metadata.sql
+
+# UI (submodule)
 ui/.eslintcache
 ui/coverage/
 ui/node_modules/
 ui/yarn-error.log
-vendor
+ui/dist/
+ui/.cache/
+
+# Build artifacts
+*.whl
+*.tar.gz
+
+# Piccolo
+piccolo_migrations/__pycache__/
+
+# MCP
+mcp_config.json
+
+# Redis dumps
+dump.rdb
+
+# Temporary files
+*.tmp
+.temp/
+
+# Documentation builds
+docs/_build/
+site/
+
+# Vendor
+vendor/