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/thumbs.go

@@ -0,0 +1,151 @@
+package gallery
+
+import (
+	"image"
+	"image/jpeg"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"golang.org/x/image/draw"
+)
+
+const (
+	gridThumbMaxEdge = 320
+	heroThumbMaxEdge = 640
+	gridThumbQuality = 75
+	heroThumbQuality = 78
+	thumbDirName     = "thumbs"
+	heroDirName      = "hero"
+)
+
+// EnsureThumbnails creates grid and hero JPEG derivatives mirroring album folders.
+func EnsureThumbnails(imagesDir string) error {
+	if err := os.MkdirAll(filepath.Join(imagesDir, thumbDirName), 0o755); err != nil {
+		return err
+	}
+	if err := os.MkdirAll(filepath.Join(imagesDir, heroDirName), 0o755); err != nil {
+		return err
+	}
+
+	return filepath.WalkDir(imagesDir, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() {
+			if d.Name() == thumbDirName || d.Name() == heroDirName {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+		if !isJPEG(d.Name()) {
+			return nil
+		}
+
+		rel, err := filepath.Rel(imagesDir, path)
+		if err != nil {
+			return err
+		}
+		rel = filepath.ToSlash(rel)
+		if !safeRelPath(rel) {
+			return nil
+		}
+
+		thumbDst := filepath.Join(imagesDir, thumbDirName, filepath.FromSlash(rel))
+		heroDst := filepath.Join(imagesDir, heroDirName, filepath.FromSlash(rel))
+		if err := os.MkdirAll(filepath.Dir(thumbDst), 0o755); err != nil {
+			return err
+		}
+		if err := os.MkdirAll(filepath.Dir(heroDst), 0o755); err != nil {
+			return err
+		}
+		if err := writeThumb(path, thumbDst, gridThumbMaxEdge, gridThumbQuality); err != nil {
+			return err
+		}
+		return writeThumb(path, heroDst, heroThumbMaxEdge, heroThumbQuality)
+	})
+}
+
+// EnsurePriority generates thumbnails for one image before first page load.
+func EnsurePriority(imagesDir, relPath string) error {
+	if !safeRelPath(relPath) || !isJPEG(filepath.Base(relPath)) {
+		return nil
+	}
+	src := filepath.Join(imagesDir, filepath.FromSlash(relPath))
+	thumbDst := filepath.Join(imagesDir, thumbDirName, filepath.FromSlash(relPath))
+	heroDst := filepath.Join(imagesDir, heroDirName, filepath.FromSlash(relPath))
+	if err := os.MkdirAll(filepath.Dir(thumbDst), 0o755); err != nil {
+		return err
+	}
+	if err := os.MkdirAll(filepath.Dir(heroDst), 0o755); err != nil {
+		return err
+	}
+	if err := writeThumb(src, heroDst, heroThumbMaxEdge, heroThumbQuality); err != nil {
+		return err
+	}
+	return writeThumb(src, thumbDst, gridThumbMaxEdge, gridThumbQuality)
+}
+
+func writeThumb(src, dst string, maxEdge, quality int) error {
+	srcInfo, err := os.Stat(src)
+	if err != nil {
+		return err
+	}
+	if dstInfo, err := os.Stat(dst); err == nil && !dstInfo.ModTime().Before(srcInfo.ModTime()) {
+		return nil
+	}
+
+	f, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	img, err := jpeg.Decode(f)
+	if err != nil {
+		return err
+	}
+
+	thumb := resizeThumb(img, maxEdge)
+	out, err := os.Create(dst)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	return jpeg.Encode(out, thumb, &jpeg.Options{Quality: quality})
+}
+
+func resizeThumb(src image.Image, maxEdge int) image.Image {
+	b := src.Bounds()
+	w, h := b.Dx(), b.Dy()
+	if w <= 0 || h <= 0 {
+		return src
+	}
+
+	scale := float64(maxEdge) / float64(w)
+	if h > w {
+		scale = float64(maxEdge) / float64(h)
+	}
+	nw := int(float64(w) * scale)
+	nh := int(float64(h) * scale)
+	if nw < 1 {
+		nw = 1
+	}
+	if nh < 1 {
+		nh = 1
+	}
+	if nw >= w && nh >= h {
+		return src
+	}
+
+	dst := image.NewRGBA(image.Rect(0, 0, nw, nh))
+	draw.CatmullRom.Scale(dst, dst.Bounds(), src, b, draw.Over, nil)
+	return dst
+}
+
+func isJPEG(name string) bool {
+	ext := strings.ToLower(filepath.Ext(name))
+	return ext == ".jpg" || ext == ".jpeg"
+}