feat: show the build commit as a faint corner mark

Declares ARG NEXT_PUBLIC_APP_COMMIT, supplied by Ship, and renders it as a
nearly transparent, click-through stamp. Renders nothing when unset.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Dockerfile

@@ -53,6 +53,11 @@ COPY . .
 ENV NEXT_TELEMETRY_DISABLED=1
 ENV NODE_ENV=production
 
+# The commit being built, supplied by Ship. Declared late so the layers above
+# stay cached; it is empty for builds that do not pass it.
+ARG NEXT_PUBLIC_APP_COMMIT
+ENV NEXT_PUBLIC_APP_COMMIT=${NEXT_PUBLIC_APP_COMMIT}
+
 # Build the standalone server. This produces `.next/standalone/` which
 # already contains the trimmed `node_modules` needed at runtime plus a
 # ready-to-run `server.js`.

src/app/layout.tsx

@@ -7,6 +7,7 @@ import "leaflet.markercluster/dist/MarkerCluster.Default.css";
 import { AuthProvider } from "@/hooks/use-auth";
 import { ThemeProvider } from "@/hooks/use-theme";
 import { PwaRegister } from "@/components/pwa-register";
+import { BuildStamp } from "@/components/build-stamp";
 
 // Every deployment uses named PocketBase sessions.
 export const dynamic = "force-dynamic";
@@ -102,6 +103,7 @@ export default function RootLayout({
           <AuthProvider mode="users">
             <PwaRegister />
             {children}
+            <BuildStamp />
           </AuthProvider>
         </ThemeProvider>
       </body>

src/components/build-stamp.tsx

@@ -0,0 +1,32 @@
+/**
+ * The commit this build came from, as a faint mark in the corner.
+ *
+ * `NEXT_PUBLIC_APP_COMMIT` is set by Ship (the Forgejo Desktop app) when it
+ * builds the image. A build made any other way has no value, so nothing is
+ * rendered. It never takes a click and is nearly transparent.
+ */
+export function BuildStamp() {
+  const commit = process.env.NEXT_PUBLIC_APP_COMMIT;
+  if (!commit) return null;
+
+  return (
+    <div
+      aria-hidden="true"
+      title={`Build ${commit}`}
+      style={{
+        position: "fixed",
+        right: 6,
+        bottom: "calc(env(safe-area-inset-bottom, 0px) + 3px)",
+        zIndex: 2147483647,
+        fontSize: 9,
+        lineHeight: 1,
+        fontFamily: "ui-monospace, SFMono-Regular, Menlo, monospace",
+        opacity: 0.3,
+        pointerEvents: "none",
+        userSelect: "none",
+      }}
+    >
+      {commit}
+    </div>
+  );
+}