Add app detail/info pages with optional config support

- New route: GET /apps/{slug} renders info page with use cases, setup guide, prerequisites
- New API: POST /api/stacks/{name}/optional-config for updating optional env vars
- New structs: AppInfo, OptionalConfigGroup, OptionalConfigField in metadata.go
- UpdateOptionalConfig saves to app.yaml and restarts deployed stacks with new env vars
- Info page template with hero section, screenshots, info cards, optional config form
- Navigation: stack cards now link to /apps/{slug}, deploy page has "Részletek" link

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/api/router.go

@@ -75,6 +75,10 @@ func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	case hasSuffix(path, "/update") && req.Method == http.MethodPost:
 		r.actionStack(w, "update", extractName(path, "/update"))
 
+	// POST /api/stacks/{name}/optional-config
+	case hasSuffix(path, "/optional-config") && req.Method == http.MethodPost:
+		r.updateOptionalConfig(w, req, extractName(path, "/optional-config"))
+
 	// GET /api/stacks/{name}/logs
 	case hasSuffix(path, "/logs") && req.Method == http.MethodGet:
 		r.getStackLogs(w, req, extractName(path, "/logs"))
@@ -210,6 +214,26 @@ func (r *Router) actionStack(w http.ResponseWriter, action, name string) {
 	writeJSON(w, http.StatusOK, apiResponse{OK: true, Message: "Stack " + name + " " + action + " completed"})
 }
 
+func (r *Router) updateOptionalConfig(w http.ResponseWriter, req *http.Request, name string) {
+	r.logger.Printf("[API] Optional config update requested for stack: %s", name)
+
+	var body struct {
+		Values map[string]string `json:"values"`
+	}
+	if err := json.NewDecoder(req.Body).Decode(&body); err != nil {
+		writeJSON(w, http.StatusBadRequest, apiResponse{OK: false, Error: "invalid request body"})
+		return
+	}
+
+	if err := r.stackMgr.UpdateOptionalConfig(name, body.Values); err != nil {
+		r.logger.Printf("[API] Optional config update failed for %s: %v", name, err)
+		writeJSON(w, http.StatusInternalServerError, apiResponse{OK: false, Error: err.Error()})
+		return
+	}
+
+	writeJSON(w, http.StatusOK, apiResponse{OK: true, Message: "Beállítások frissítve"})
+}
+
 func (r *Router) getStackLogs(w http.ResponseWriter, req *http.Request, name string) {
 	lines := 100
 	if v := req.URL.Query().Get("lines"); v != "" {