feat(server,web): expose server version via /healthz + display in Settings

Came up debugging the in-app update flow — wasn't obvious which image
the container was actually running without exec'ing in. New flow:

### Server
- internal/server/version.go: new `var ServerVersion = "dev"`,
  overridden via -ldflags at build time.
- /healthz response gains a "version" key alongside the existing
  "status" + "min_client_version". Backward-compat: existing clients
  ignore unknown JSON fields. Endpoint stays unauthenticated.

### Build
- Dockerfile: new `ARG MINSTREL_VERSION=dev`, threaded into the
  go build -ldflags so the binary's ServerVersion is stamped at
  link time. Default "dev" preserves local `docker build` ergonomics.
- .forgejo/workflows/release.yml: tags step also emits a `version`
  output (the git tag for tag pushes, "main" for branch pushes);
  build step passes it as `--build-arg MINSTREL_VERSION=...`.

### Web
- web/src/lib/components/ServerVersion.svelte: small understated
  text ("Server v2026.05.10.2") that fetches /healthz on mount.
  Renders nothing on parse failure or pre-version images.
- Mounted at the bottom of Settings.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.forgejo/workflows/release.yml

@@ -50,9 +50,11 @@ jobs:
           if [[ "${GITHUB_REF}" == refs/tags/v* ]]; then
             VERSION="${GITHUB_REF#refs/tags/}"
             echo "args=-t ${IMAGE}:${VERSION} -t ${IMAGE}:latest" >> "$GITHUB_OUTPUT"
+            echo "version=${VERSION}" >> "$GITHUB_OUTPUT"
             echo "::notice::Release build: ${VERSION} + latest"
           else
             echo "args=-t ${IMAGE}:main" >> "$GITHUB_OUTPUT"
+            echo "version=main" >> "$GITHUB_OUTPUT"
             echo "::notice::Main-branch build: :main"
           fi
 
@@ -93,4 +95,7 @@ jobs:
 
       - name: Build and push
         if: steps.guard.outputs.ready == 'true'
-        run: docker buildx build --push ${{ steps.tags.outputs.args }} .
+        run: |
+          docker buildx build \
+            --build-arg MINSTREL_VERSION="${{ steps.tags.outputs.version }}" \
+            --push ${{ steps.tags.outputs.args }} .

Dockerfile

@@ -15,7 +15,13 @@ COPY . .
 # Overwrite the committed placeholder with the freshly-built SPA assets.
 COPY --from=web /web/build ./web/build
 ENV CGO_ENABLED=0
-RUN go build -trimpath -ldflags="-s -w" -o /out/minstrel ./cmd/minstrel
+# Version stamping: release.yml passes the git tag via MINSTREL_VERSION
+# build-arg; local `docker build` falls back to "dev". Surfaced at
+# /healthz for operator-side image-version verification.
+ARG MINSTREL_VERSION=dev
+RUN go build -trimpath \
+    -ldflags="-s -w -X 'git.fabledsword.com/bvandeusen/minstrel/internal/server.ServerVersion=${MINSTREL_VERSION}'" \
+    -o /out/minstrel ./cmd/minstrel
 
 FROM debian:bookworm-slim
 RUN apt-get update \

internal/server/server.go

@@ -148,6 +148,7 @@ func (s *Server) handleHealthz(w http.ResponseWriter, _ *http.Request) {
 	w.WriteHeader(http.StatusOK)
 	_ = json.NewEncoder(w).Encode(map[string]string{
 		"status":             "ok",
+		"version":            ServerVersion,
 		"min_client_version": MinClientVersion,
 	})
 }

internal/server/version.go

@@ -4,3 +4,13 @@ package server
 // accepts. Bump it when a server change requires a paired client update;
 // older clients see version_too_old at /healthz and refuse to operate.
 const MinClientVersion = "0.1.0"
+
+// ServerVersion is the deployed server image's version tag. Defaults to
+// "dev" for local builds; overridden at link time via:
+//
+//   -ldflags="-X 'git.fabledsword.com/bvandeusen/minstrel/internal/server.ServerVersion=v2026.05.10.2'"
+//
+// release.yml passes the git tag through MINSTREL_VERSION build-arg →
+// Dockerfile ldflag. Surfaced at /healthz so operators can verify which
+// image their container is running without exec'ing into it.
+var ServerVersion = "dev"

web/src/lib/components/ServerVersion.svelte

@@ -0,0 +1,37 @@
+<script lang="ts">
+  import { onMount } from 'svelte';
+
+  // Reads /healthz on mount and surfaces the deployed server version
+  // as understated text. Useful when verifying which image a container
+  // is actually running (came up debugging the in-app update flow when
+  // it wasn't obvious whether v2026.05.10.0 or .1 was deployed).
+  //
+  // /healthz is unauthenticated, so the bare fetch works without
+  // credentials. Renders nothing on parse failure or pre-version
+  // images that don't include the field — graceful degradation.
+
+  type Health = { status: string; version?: string };
+
+  let version = $state<string | null>(null);
+
+  onMount(async () => {
+    try {
+      const res = await fetch('/healthz');
+      if (!res.ok) return;
+      const body = (await res.json()) as Partial<Health>;
+      if (body.version && body.version !== 'dev') {
+        version = body.version;
+      } else if (body.version === 'dev') {
+        // Local dev images report "dev" — show it so the operator
+        // can tell they're not on a release tag.
+        version = 'dev';
+      }
+    } catch {
+      // network / parse error — silent.
+    }
+  });
+</script>
+
+{#if version}
+  <p class="text-xs text-text-secondary">Server {version}</p>
+{/if}

web/src/routes/settings/+page.svelte

@@ -18,6 +18,7 @@
   import { errCode } from '$lib/api/errors';
   import { pushToast } from '$lib/stores/toast.svelte';
   import MobileAppDownload from '$lib/components/MobileAppDownload.svelte';
+  import ServerVersion from '$lib/components/ServerVersion.svelte';
 
   const queryClient = useQueryClient();
 
@@ -326,4 +327,8 @@
   </section>
 
   <MobileAppDownload />
+
+  <div class="pt-2 text-center">
+    <ServerVersion />
+  </div>
 </div>