Bilder-Download: Mehrfach-Auswahl + Ordner-ZIP

- Selection-Mode: Bilder in Galerie per Klick auswaehlen
- 1-3 Bilder: einzeln herunterladen, 4+: als ZIP
- Ordner-Download: ganzen zugewiesenen Ordner als ZIP
- Sicherheit: Zugriffspruefung + Path-Traversal-Schutz
- archiver Package fuer Streaming-ZIP-Erstellung

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

assets/sass/custom.scss

@@ -6,6 +6,85 @@
 	color: _palette(fg);
 }
 
+/* ==================== Selection Mode ==================== */
+
+#selection-toolbar {
+	position: fixed;
+	bottom: _size(header);
+	left: 0;
+	width: 100%;
+	background: rgba(31, 34, 36, 0.95);
+	padding: 0.75em 1.5em;
+	display: flex;
+	align-items: center;
+	gap: 1em;
+	z-index: _misc(z-index-base) + 3;
+	transform: translateY(100%);
+	transition: transform 0.3s ease;
+	box-sizing: border-box;
+
+	&.visible {
+		transform: translateY(0);
+	}
+
+	#sel-count {
+		color: _palette(fg-bold);
+		font-weight: _font(weight-extrabold);
+		margin-right: auto;
+		white-space: nowrap;
+	}
+
+	button {
+		white-space: nowrap;
+	}
+}
+
+body.selection-mode {
+	#main .thumb {
+		cursor: pointer;
+		position: relative;
+
+		&::before {
+			content: '';
+			position: absolute;
+			top: 0.6em;
+			left: 0.6em;
+			width: 1.4em;
+			height: 1.4em;
+			border: 2px solid rgba(255, 255, 255, 0.7);
+			border-radius: 3px;
+			background: rgba(0, 0, 0, 0.4);
+			z-index: 2;
+			transition: all 0.2s ease;
+			pointer-events: none;
+		}
+
+		&.selected {
+			&::before {
+				background: _palette(accent1);
+				border-color: _palette(accent1);
+			}
+
+			.image {
+				outline: 3px solid _palette(accent1);
+				outline-offset: -3px;
+			}
+		}
+	}
+}
+
+@media screen and (max-width: 736px) {
+	#selection-toolbar {
+		bottom: auto;
+		top: _size(header);
+		transform: translateY(-200%);
+
+		&.visible {
+			transform: translateY(0);
+		}
+	}
+}
+
 /* Footer */
 #footer {
 	.presentify {