Settings: 'About & updates' — check-for-updates against the forgejo repo

Bakes the source commit + build timestamp into the jar
(generateBuildInfo task -> shonar-build.properties on the classpath).
The Settings screen gains a 'Check for updates' button that queries the
anonymous Forgejo commits API for the latest master commit and compares
it to this build: up to date / update available (with commit shas and an
'Open repo' link via xdg-open) / 'newer than forgejo — local work not
yet pushed' for dev builds ahead of the remote. Network failures render
as a message with a repo link, never a crash.

Gate: :app:compileKotlin + :app:test green (9 suites); jar property
verified by unzip.

app/build.gradle.kts

@@ -33,6 +33,32 @@ sourceSets {
     }
 }
 
+// Bake the source commit + build time into the jar so the in-app
+// check-for-updates can tell "this build is current" from "the repo has
+// newer work". Lives on outputs so a new commit invalidates it.
+val generateBuildInfo = tasks.register("generateBuildInfo") {
+    val outDir = layout.buildDirectory.dir("generated/shonar/resources")
+    outputs.dir(outDir)
+    val commit = providers.exec {
+        commandLine("git", "-C", rootProject.projectDir.absolutePath,
+            "rev-parse", "--short", "HEAD")
+    }.standardOutput.asText.map { it.trim() }
+    doLast {
+        val dir = outDir.get().asFile
+        dir.mkdirs()
+        File(dir, "shonar-build.properties").writeText(
+            "commit=${commit.get().ifBlank { "unknown" }}\n" +
+            "builtAt=${System.currentTimeMillis()}\n",
+        )
+    }
+}
+
+sourceSets {
+    main {
+        resources.srcDir(generateBuildInfo)
+    }
+}
+
 dependencies {
     implementation(compose.desktop.currentOs)
     implementation(compose.material3)