Add Technical Kiwi website with Go, templ, and HTMX.

Single-page site with gallery by album and event, contact form over SMTP,
Docker dev/prod setup, and on-server image derivatives. Gallery photos stay
local (app/images/ is gitignored).

Co-authored-by: Cursor <cursoragent@cursor.com>

app/templates/helpers.go

@@ -0,0 +1,7 @@
+package templates
+
+import "time"
+
+func currentYear() string {
+	return time.Now().Format("2006")
+}