feat: Initial Hub implementation

Complete LetsBe Hub service for license management and telemetry:

- Client and Instance CRUD APIs
- License key generation and validation (lb_inst_ format)
- Hub API key generation (hk_ format) for telemetry auth
- Instance activation endpoint
- Telemetry collection with privacy-first redactor
- Key rotation and suspend/reactivate functionality
- Alembic migrations for PostgreSQL
- Docker Compose deployment ready
- Comprehensive test suite

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

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+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# Virtual environments
+.venv/
+venv/
+ENV/
+
+# Environment files
+.env
+!.env.example
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# Testing
+.pytest_cache/
+.coverage
+htmlcov/
+
+# Build
+dist/
+build/
+*.egg-info/
+
+# Database
+*.db
+*.sqlite3
+
+# Logs
+*.log