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>

Dockerfile.dev

@@ -0,0 +1,18 @@
+ARG GO_VERSION=1.25
+FROM golang:${GO_VERSION}-bookworm
+
+RUN go install github.com/a-h/templ/cmd/templ@latest \
+	&& go install github.com/air-verse/air@latest
+
+WORKDIR /app
+
+COPY app/go.mod app/go.sum ./
+RUN go mod download
+
+COPY app/.air.toml app/dev.sh ./
+RUN chmod +x dev.sh
+
+EXPOSE 8080 7331
+ENV ADDR=:8080
+
+CMD ["./dev.sh"]