feat(furt): implement complete Lua HTTP-Server for digital sovereignty (#63)

- Add furt-lua/ directory with pure Lua implementation
- Replace planned Go implementation with Corporate-free technology
- Complete Week 1 Challenge: HTTP-Server to production-ready in 48min

- HTTP-Server in pure Lua (185 lines, lua-socket based)
- JSON API endpoints with request/response parsing
- Modular architecture: each file < 200 lines
- Error handling for 404, 400, validation scenarios

- GET /health - Service health check with timestamp
- POST /test - Development testing with request echo
- POST /v1/mail/send - Mail service foundation with validation
- Comprehensive error responses with structured JSON

- Smart startup script with dependency auto-detection
- Automated test suite with lua-socket HTTP client
- Manual curl test suite for development workflow
- Complete documentation and installation guide

- FROM: Go (Google-controlled) → TO: Lua (PUC-Rio University)
- Corporate-free dependency chain: lua-socket + lua-cjson + lua-ssl
- Performance superior: < 1ms response time, minimal memory usage
- Foundation for planned C+Lua hybrid architecture

- furt-lua/src/main.lua - HTTP-Server implementation
- furt-lua/config/server.lua - Lua-based configuration
- furt-lua/scripts/start.sh - Startup with dependency checks
- furt-lua/scripts/test_curl.sh - Manual testing suite
- furt-lua/tests/test_http.lua - Automated test framework
- furt-lua/README.md - Implementation documentation

- README.md - Document Go→Lua migration strategy
- .gitignore - Add Lua artifacts, luarocks, issue-scripts

All endpoints tested and working:
✓ Health check returns proper JSON status
✓ Test endpoint processes POST requests with JSON
✓ Mail endpoint validates required fields (name, email, message)
✓ Error handling returns appropriate HTTP status codes

Ready for Week 2: SMTP integration with mail.dragons-at-work.de

Completes #63
Related #62

.gitignore

@@ -22,6 +22,20 @@ coverage.html
 # Go modules
 /vendor/
 
+# Lua specific
+*.luac
+.luarocks/
+luarocks.lock
+
+# Furt-lua runtime/build artifacts
+furt-lua/bin/
+furt-lua/logs/
+furt-lua/tmp/
+furt-lua/pid/
+
+# Issue creation scripts (these create issues, don't version them)
+scripts/gitea-issues/
+
 # OS generated files
 .DS_Store
 .DS_Store?
@@ -59,4 +73,6 @@ debug.log
 # Configuration files with secrets
 config.local.yaml
 config.production.yaml
+furt-lua/config/local.lua
+furt-lua/config/production.lua