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/internal/gallery/path.go

@@ -0,0 +1,59 @@
+package gallery
+
+import (
+	"net/url"
+	"regexp"
+	"strings"
+)
+
+var zipExportSuffix = regexp.MustCompile(`-\d{8}T\d{6}Z-1-\d+$`)
+
+// URLPath escapes a relative image path for use in URL paths.
+func URLPath(rel string) string {
+	parts := strings.Split(rel, "/")
+	for i, p := range parts {
+		parts[i] = url.PathEscape(p)
+	}
+	return strings.Join(parts, "/")
+}
+
+func collectionFromRel(rel string) (key, label string) {
+	parts := strings.Split(rel, "/")
+	if len(parts) <= 2 {
+		return "", ""
+	}
+	inner := strings.TrimSpace(parts[len(parts)-2])
+	label = cleanCollectionName(inner)
+	if label == "" {
+		return "", ""
+	}
+	return collectionKey(label), label
+}
+
+func cleanCollectionName(name string) string {
+	name = strings.TrimSpace(name)
+	name = zipExportSuffix.ReplaceAllString(name, "")
+	return strings.TrimSpace(name)
+}
+
+func collectionKey(label string) string {
+	key := strings.ToLower(label)
+	key = strings.ReplaceAll(key, " ", "-")
+	key = strings.Map(func(r rune) rune {
+		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '-' {
+			return r
+		}
+		return -1
+	}, key)
+	return key
+}
+
+// CollectionLabel returns display name for a collection filter key.
+func CollectionLabel(key string, images []Image) string {
+	for _, img := range images {
+		if img.CollectionKey == key {
+			return img.Collection
+		}
+	}
+	return key
+}