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/.air.toml

@@ -0,0 +1,18 @@
+root = "."
+tmp_dir = "tmp"
+
+[build]
+  cmd = "templ generate --notify-proxy && go build -o ./tmp/main ./cmd/server"
+  entrypoint = ["./tmp/main"]
+  delay = 300
+  exclude_dir = ["tmp", "bin", "images", "vendor", "testdata"]
+  exclude_regex = ["_templ.go"]
+  include_ext = ["go", "css"]
+  send_interrupt = true
+  stop_on_error = true
+
+[log]
+  time = true
+
+[misc]
+  clean_on_exit = true