refactor: Separate CV domain and UI presentation models into distinct packages

**Main Changes:**

1. **Package Restructuring** - Separated mixed concerns into focused packages:
   - Created `internal/models/cv/` for CV domain logic (CV, Personal, Experience, etc.)
   - Created `internal/models/ui/` for UI presentation logic (InfoModal, ShortcutsModal, etc.)
   - Removed monolithic `internal/models/cv.go` (300+ lines → organized packages)

2. **Testing** - Added comprehensive unit tests:
   - `internal/models/cv/loader_test.go` - CV data loading and validation
   - `internal/models/ui/loader_test.go` - UI translations loading
   - All tests passing ✅

3. **Documentation** - Added Go learning knowledge base:
   - `_go-learning/architecture/server-design.md` - Goroutines, graceful shutdown explained
   - `_go-learning/refactorings/001-cv-model-separation.md` - This refactoring documented
   - Public documentation showcasing Go expertise (README.md kept private)

4. **Handler Updates** - Updated imports to use new package structure:
   - `internal/handlers/cv.go` - Uses `cvmodel` and `uimodel` aliases

**Benefits:**
- ✅ Clear separation of concerns (domain vs presentation)
- ✅ Better testability (isolated package testing)
- ✅ Improved maintainability (smaller, focused files)
- ✅ Scalability (each domain can evolve independently)
- ✅ Follows Go best practices (small, cohesive packages)

**Other Updates:**
- Updated middleware security checks
- Template improvements
- Organized completed prompts

**Testing:**
- All Go unit tests pass (cv, ui, handlers)
- Server verified with curl tests (English, Spanish, Health endpoints)
- Frontend functionality unchanged (refactoring is transparent to UI)

.gitignore

@@ -56,3 +56,6 @@ playwright.config.js
 
 # Test artifacts
 tests/screenshots/
+
+# Personal learning documentation README (private goals and notes)
+_go-learning/README.md