feat(manage): delete photos from /manage, prune leftover pages

/manage/delete/{slug} asks for confirmation, then removes the image,
its sidecar and everything generated from them. Builds now drop day
pages of days without photos and pager pages past the last one, so a
delete or a date change leaves nothing behind.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

generator_test.go

@@ -123,3 +123,36 @@ func TestSwitchingDefaultViewDropsOldViewDir(t *testing.T) {
 		t.Errorf("site root is still the timeline")
 	}
 }
+
+func TestShrinkingSiteDropsLeftoverPages(t *testing.T) {
+	output := t.TempDir()
+	buildSite(t, output, viewTimeline) // three photos, page size two
+
+	content := t.TempDir()
+	var img bytes.Buffer
+	if err := jpeg.Encode(&img, image.NewRGBA(image.Rect(0, 0, 8, 8)), nil); err != nil {
+		t.Fatal(err)
+	}
+	writeFile(t, filepath.Join(content, "one.jpg"), img.Bytes())
+	writeFile(t, filepath.Join(content, "one.toml"),
+		[]byte("caption = \"one\"\ndate = \"2026-06-14\"\n"))
+
+	// The same output directory, now fed a single photo: one page per view,
+	// one day.
+	g := NewGenerator(content, output, "https://photos.example.com",
+		"Ada", "", "", "", "", "Crimson Pro", "Manjari", 2, viewTimeline)
+	if err := g.Build(); err != nil {
+		t.Fatal(err)
+	}
+
+	for _, gone := range []string{"page/2", "grid/page/2", "day/2026-06-10"} {
+		if _, err := os.Stat(filepath.Join(output, filepath.FromSlash(gone))); !os.IsNotExist(err) {
+			t.Errorf("leftover %s survived", gone)
+		}
+	}
+	for _, kept := range []string{"index.html", "grid/index.html", "day/2026-06-14/index.html"} {
+		if _, err := os.Stat(filepath.Join(output, filepath.FromSlash(kept))); err != nil {
+			t.Errorf("%s is missing: %v", kept, err)
+		}
+	}
+}