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)

internal/models/ui/loader.go

@@ -0,0 +1,56 @@
+package ui
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+)
+
+// LoadUI loads UI translations from a JSON file for the specified language
+func LoadUI(lang string) (*UI, error) {
+	if lang != "en" && lang != "es" {
+		return nil, fmt.Errorf("unsupported language: %s", lang)
+	}
+
+	filename := fmt.Sprintf("data/ui-%s.json", lang)
+	filepath, err := findDataFile(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	data, err := os.ReadFile(filepath)
+	if err != nil {
+		return nil, fmt.Errorf("error reading file %s: %w", filename, err)
+	}
+
+	var uiData UI
+	if err := json.Unmarshal(data, &uiData); err != nil {
+		return nil, fmt.Errorf("error parsing JSON: %w", err)
+	}
+
+	return &uiData, nil
+}
+
+// findDataFile locates a data file by searching up the directory tree
+func findDataFile(filename string) (string, error) {
+	// Try current directory first
+	if _, err := os.Stat(filename); err == nil {
+		return filename, nil
+	}
+
+	// Try parent directories (for tests running from subdirectories)
+	paths := []string{
+		filename,               // Current dir
+		"../" + filename,       // One level up
+		"../../" + filename,    // Two levels up (for tests in internal/handlers)
+		"../../../" + filename, // Three levels up
+	}
+
+	for _, path := range paths {
+		if _, err := os.Stat(path); err == nil {
+			return path, nil
+		}
+	}
+
+	return "", fmt.Errorf("file not found: %s (searched: current dir, ../, ../../, ../../../)", filename)
+}