Refactor template rendering with Renderer interface for testability

Introduce a Renderer interface to abstract template rendering, enabling
tests to use MockRenderer instead of requiring real template files.

Changes:
- Add renderer.go with Renderer interface, TemplateRenderer, and MockRenderer
- Update Handler struct to use Renderer instead of *template.Template
- Update HTMLResponse() to accept Renderer interface
- Replace all h.templates.ExecuteTemplate() calls with h.renderer.Render()
- Update all tests to use MockRenderer, removing template file dependencies

This eliminates 15+ tests that previously skipped with "Templates not
available" and improves test isolation.

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

1 files changed, 2 insertions, 3 deletions

diff --git a/internal/handlers/response.go b/internal/handlers/response.go
index 34d4491..679a452 100644
--- a/internal/handlers/response.go
+++ b/internal/handlers/response.go
@@ -2,7 +2,6 @@ package handlers
 
 import (
 	"encoding/json"
-	"html/template"
 	"log"
 	"net/http"
 )
@@ -30,10 +29,10 @@ func JSONError(w http.ResponseWriter, status int, msg string, err error) {
 }
 
 // HTMLResponse renders an HTML template
-func HTMLResponse(w http.ResponseWriter, tmpl *template.Template, name string, data interface{}) {
+func HTMLResponse(w http.ResponseWriter, r Renderer, name string, data interface{}) {
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
 	noCacheHeaders(w)
-	if err := tmpl.ExecuteTemplate(w, name, data); err != nil {
+	if err := r.Render(w, name, data); err != nil {
 		http.Error(w, "Failed to render template", http.StatusInternalServerError)
 		log.Printf("Error rendering template %s: %v", name, err)
 	}