feat: rename service to galo, add halo branding and release build

- rename Go module, binary, systemd unit, PG_DATABASE default, frontend package and docs from shared-album to galo
- add theme-aware halo emblem and favicon (new ui-branding capability)
- add make build-release (versioned, stripped, static binary) and run the binary from the repo root

frontend/static/favicon.svg

@@ -0,0 +1,30 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
+	<style>
+		.bg {
+			fill: #ffffff;
+		}
+		.disc {
+			fill: #2563eb;
+		}
+		.ring {
+			fill: none;
+			stroke: #2563eb;
+			stroke-opacity: 0.45;
+		}
+		@media (prefers-color-scheme: dark) {
+			.bg {
+				fill: #171717;
+			}
+			.disc {
+				fill: #60a5fa;
+			}
+			.ring {
+				stroke: #60a5fa;
+				stroke-opacity: 0.6;
+			}
+		}
+	</style>
+	<rect class="bg" width="64" height="64" rx="14" />
+	<circle class="disc" cx="32" cy="32" r="13" />
+	<circle class="ring" cx="32" cy="32" r="24" stroke-width="6" />
+</svg>