fix(ui): show version+SHA+build time in footer; fix env not reaching runtime image

PUBLIC_BUILD_VERSION and PUBLIC_BUILD_COMMIT were set only in the builder
stage ENV — they were never re-declared in the runtime stage, so the Node
server started with them undefined and the badge always showed 'dev'.

Fix: re-declare all three ARGs after the second FROM and set runtime ENVs.
Add PUBLIC_BUILD_TIME (ISO timestamp from gitea.event.head_commit.timestamp)
injected via build-arg in release.yaml. Badge now shows e.g.:
  v2.3.9+abc1234 · 28 Mar 2026 14:30 UTC

ui/Dockerfile

@@ -14,10 +14,12 @@ COPY . .
 # Build-time version info — injected by docker-compose or CI via --build-arg.
 ARG BUILD_VERSION=dev
 ARG BUILD_COMMIT=unknown
+ARG BUILD_TIME=unknown
 
 # Expose as PUBLIC_ env vars so SvelteKit's $env/dynamic/public can read them.
 ENV PUBLIC_BUILD_VERSION=$BUILD_VERSION
 ENV PUBLIC_BUILD_COMMIT=$BUILD_COMMIT
+ENV PUBLIC_BUILD_TIME=$BUILD_TIME
 
 RUN npm run build
 
@@ -40,5 +42,16 @@ ENV NODE_ENV=production
 ENV PORT=3000
 ENV HOST=0.0.0.0
 
+# Carry build-time metadata into the runtime image so the UI footer can
+# display the version, commit SHA, and build timestamp.
+# These must be re-declared after the second FROM — ARG values do not
+# cross stage boundaries, but ENV values set here persist at runtime.
+ARG BUILD_VERSION=dev
+ARG BUILD_COMMIT=unknown
+ARG BUILD_TIME=unknown
+ENV PUBLIC_BUILD_VERSION=$BUILD_VERSION
+ENV PUBLIC_BUILD_COMMIT=$BUILD_COMMIT
+ENV PUBLIC_BUILD_TIME=$BUILD_TIME
+
 EXPOSE $PORT
 CMD ["node", "build"]

ui/src/routes/+layout.svelte

@@ -433,7 +433,15 @@
 			<a href="/dmca" class="hover:text-zinc-500 transition-colors">DMCA</a>
 			<span>&copy; {new Date().getFullYear()} libnovel</span>
 		</div>
-		<!-- Build version / commit SHA -->
+		<!-- Build version / commit SHA / build time -->
+		{#snippet buildTime()}
+			{#if env.PUBLIC_BUILD_TIME && env.PUBLIC_BUILD_TIME !== 'unknown'}
+				{@const d = new Date(env.PUBLIC_BUILD_TIME)}
+				<span class="text-zinc-500" title="Build time">
+					· {d.toUTCString().replace(' GMT', ' UTC').replace(/:\d\d /, ' ')}
+				</span>
+			{/if}
+		{/snippet}
 		<div class="text-xs tabular-nums font-mono px-2 py-0.5 rounded bg-zinc-800 border border-zinc-700">
 			{#if env.PUBLIC_BUILD_VERSION && env.PUBLIC_BUILD_VERSION !== 'dev'}
 				<span class="text-zinc-300" title="Build version">{env.PUBLIC_BUILD_VERSION}</span>
@@ -442,6 +450,7 @@
 						>+{env.PUBLIC_BUILD_COMMIT.slice(0, 7)}</span
 					>
 				{/if}
+				{@render buildTime()}
 			{:else}
 				<span class="text-zinc-400">dev</span>
 			{/if}