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/dev.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+set -e
+
+# Browser: http://localhost:7331 (proxy injects auto-reload)
+# App:     http://127.0.0.1:8080 (internal, via proxy)
+exec templ generate --watch \
+	--proxy="http://127.0.0.1:8080" \
+	--proxybind="0.0.0.0" \
+	--proxyport="7331" \
+	--open-browser=false \
+	--cmd="air -c .air.toml"