refactor: simplify toggle handlers to return 204 No Content

Remove empty toggle templates (length-toggle.html, theme-toggle.html,
logo-toggle.html) that were just placeholders. The frontend uses
hx-swap="none" so the response body was always ignored anyway.

Now the handlers:
- Set the preference cookie
- Return 204 No Content immediately
- Hyperscript handles the UI state toggle on the frontend

This removes unnecessary template rendering overhead and cleans up
dead code. Tests updated to expect 204 instead of 200.

internal/handlers/cv_htmx.go

@@ -32,35 +32,9 @@ func (h *CVHandler) ToggleLength(w http.ResponseWriter, r *http.Request) {
 	// Save new state
 	middleware.SetPreferenceCookie(w, "cv-length", newLength)
 
-	// Get language from query or use current preference
-	lang := r.URL.Query().Get("lang")
-	if lang == "" {
-		lang = prefs.CVLanguage
-	}
-
-	// Prepare template data with length state
-	cvLengthClass := "cv-short"
-	if newLength == "long" {
-		cvLengthClass = "cv-long"
-	}
-
-	data := map[string]interface{}{
-		"Lang":          lang,
-		"CVLengthClass": cvLengthClass,
-	}
-
-	// Render length-toggle template with out-of-band swaps
-	tmpl, err := h.templates.Render("length-toggle.html")
-	if err != nil {
-		HandleError(w, r, TemplateError(err, "length-toggle.html"))
-		return
-	}
-
-	w.Header().Set("Content-Type", "text/html; charset=utf-8")
-	if err := tmpl.Execute(w, data); err != nil {
-		HandleError(w, r, TemplateError(err, "length-toggle.html"))
-		return
-	}
+	// Return 204 No Content - frontend uses hx-swap="none" so response body is ignored
+	// The cookie is set and hyperscript handles the UI state toggle
+	w.WriteHeader(http.StatusNoContent)
 }
 
 // ToggleIcons handles icon visibility toggle using atomic out-of-band swaps
@@ -83,30 +57,9 @@ func (h *CVHandler) ToggleIcons(w http.ResponseWriter, r *http.Request) {
 	// Save new state
 	middleware.SetPreferenceCookie(w, "cv-icons", newIcons)
 
-	// Get language from query or use current preference
-	lang := r.URL.Query().Get("lang")
-	if lang == "" {
-		lang = prefs.CVLanguage
-	}
-
-	// Prepare template data with logo state
-	data := map[string]interface{}{
-		"Lang":      lang,
-		"ShowIcons": (newIcons == "show"),
-	}
-
-	// Render logo-toggle template with out-of-band swaps
-	tmpl, err := h.templates.Render("logo-toggle.html")
-	if err != nil {
-		HandleError(w, r, TemplateError(err, "logo-toggle.html"))
-		return
-	}
-
-	w.Header().Set("Content-Type", "text/html; charset=utf-8")
-	if err := tmpl.Execute(w, data); err != nil {
-		HandleError(w, r, TemplateError(err, "logo-toggle.html"))
-		return
-	}
+	// Return 204 No Content - frontend uses hx-swap="none" so response body is ignored
+	// The cookie is set and hyperscript handles the UI state toggle
+	w.WriteHeader(http.StatusNoContent)
 }
 
 // SwitchLanguage handles language switching with atomic updates
@@ -181,28 +134,7 @@ func (h *CVHandler) ToggleTheme(w http.ResponseWriter, r *http.Request) {
 	// Save new state
 	middleware.SetPreferenceCookie(w, "cv-theme", newTheme)
 
-	// Get language from query or use current preference
-	lang := r.URL.Query().Get("lang")
-	if lang == "" {
-		lang = prefs.CVLanguage
-	}
-
-	// Prepare template data with theme state
-	data := map[string]interface{}{
-		"Lang":       lang,
-		"ThemeClean": (newTheme == "clean"),
-	}
-
-	// Render theme-toggle template with out-of-band swaps
-	tmpl, err := h.templates.Render("theme-toggle.html")
-	if err != nil {
-		HandleError(w, r, TemplateError(err, "theme-toggle.html"))
-		return
-	}
-
-	w.Header().Set("Content-Type", "text/html; charset=utf-8")
-	if err := tmpl.Execute(w, data); err != nil {
-		HandleError(w, r, TemplateError(err, "theme-toggle.html"))
-		return
-	}
+	// Return 204 No Content - frontend uses hx-swap="none" so response body is ignored
+	// The cookie is set and hyperscript handles the UI state toggle
+	w.WriteHeader(http.StatusNoContent)
 }

internal/handlers/cv_htmx_test.go

@@ -60,8 +60,9 @@ func TestToggleLength(t *testing.T) {
 			w := httptest.NewRecorder()
 			handler.ToggleLength(w, req)
 
-			if w.Code != http.StatusOK {
-				t.Errorf("Expected status OK, got %d", w.Code)
+			// 204 No Content - frontend uses hx-swap="none" so response body is ignored
+			if w.Code != http.StatusNoContent {
+				t.Errorf("Expected status No Content (204), got %d", w.Code)
 			}
 
 			// Check that response sets the toggled cookie
@@ -131,8 +132,9 @@ func TestToggleIcons(t *testing.T) {
 			w := httptest.NewRecorder()
 			handler.ToggleIcons(w, req)
 
-			if w.Code != http.StatusOK {
-				t.Errorf("Expected status OK, got %d", w.Code)
+			// 204 No Content - frontend uses hx-swap="none" so response body is ignored
+			if w.Code != http.StatusNoContent {
+				t.Errorf("Expected status No Content (204), got %d", w.Code)
 			}
 		})
 	}
@@ -253,8 +255,9 @@ func TestToggleTheme(t *testing.T) {
 			w := httptest.NewRecorder()
 			handler.ToggleTheme(w, req)
 
-			if w.Code != http.StatusOK {
-				t.Errorf("Expected status OK, got %d", w.Code)
+			// 204 No Content - frontend uses hx-swap="none" so response body is ignored
+			if w.Code != http.StatusNoContent {
+				t.Errorf("Expected status No Content (204), got %d", w.Code)
 			}
 
 			// Verify theme cookie was set