Fix timeline calendar view and shopping UI bugs (#56, #65-73)

- #56: Add overflow-hidden to card/panel classes to prevent content overflow
- #65: Fix Google Tasks not showing by including tasks without due dates
- #66: Add no-cache headers to prevent stale template responses
- #67: Increase dropdown z-index to 100 for proper layering
- #69: Implement calendar-style Today section with hourly grid (6am-10pm),
       duration-based event heights, and compact overdue/all-day section
- #70: Only reset shopping-mode form on successful submission
- #71: Remove checkboxes from shopping tab (only show in shopping mode)
- #72: Add inline add-item input at end of each store section
- #73: Add Grouped/Flat view toggle for shopping list

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

1 files changed, 10 insertions, 0 deletions

diff --git a/internal/handlers/response.go b/internal/handlers/response.go
index 9a7ab45..34d4491 100644
--- a/internal/handlers/response.go
+++ b/internal/handlers/response.go
@@ -7,9 +7,17 @@ import (
 	"net/http"
 )
 
+// noCacheHeaders sets headers to prevent browser caching
+func noCacheHeaders(w http.ResponseWriter) {
+	w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
+	w.Header().Set("Pragma", "no-cache")
+	w.Header().Set("Expires", "0")
+}
+
 // JSONResponse writes data as JSON with appropriate headers
 func JSONResponse(w http.ResponseWriter, data interface{}) {
 	w.Header().Set("Content-Type", "application/json")
+	noCacheHeaders(w)
 	_ = json.NewEncoder(w).Encode(data)
 }
 
@@ -23,6 +31,8 @@ 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{}) {
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	noCacheHeaders(w)
 	if err := tmpl.ExecuteTemplate(w, name, data); err != nil {
 		http.Error(w, "Failed to render template", http.StatusInternalServerError)
 		log.Printf("Error rendering template %s: %v", name, err)