Add CalVer build-time version tracking

- Dockerfile: ARG BUILD_VERSION=dev → ENV APP_VERSION baked into image
- ci.yml: BUILD_VERSION passed as build-arg; set to git tag name on v*
  tag builds, "dev" on branch builds
- routes/api.py: GET /api/version returns {"version": APP_VERSION}
- SettingsView: fetches /api/version on mount, displays in About section
  under General tab

Version source of truth is the git tag (YY.MM.DD.N CalVer).
pyproject.toml / package.json versions are no longer maintained.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/views/SettingsView.vue

@@ -28,6 +28,7 @@ const saving = ref(false);
 const saved = ref(false);
 const exporting = ref(false);
 const restoring = ref(false);
+const appVersion = ref('dev');
 const restoreFileInput = ref<HTMLInputElement | null>(null);
 
 // Migrate stored "admin" → "config"; unknown tabs fall back to "general"
@@ -176,6 +177,10 @@ const searchLoading = ref(false);
 const searchError = ref("");
 
 onMounted(async () => {
+  try {
+    const v = await apiGet<{ version: string }>('/api/version')
+    appVersion.value = v.version
+  } catch { /* non-critical */ }
   await store.fetchSettings();
   pushStore.checkSubscription();
   assistantName.value = store.assistantName;
@@ -1031,6 +1036,11 @@ function formatUserDate(iso: string): string {
         </div>
       </section>
 
+      <section class="settings-section full-width">
+        <h2>About</h2>
+        <p class="version-line">Fabled Assistant <span class="version-badge">{{ appVersion }}</span></p>
+      </section>
+
     </div>
 
     <!-- ── Integrations ── -->
@@ -2206,6 +2216,25 @@ function formatUserDate(iso: string): string {
   margin-right: 0.25rem;
 }
 
+/* ── About / version ─────────────────────────────────────────── */
+.version-line {
+  margin: 0;
+  font-size: 0.9rem;
+  color: var(--color-text-secondary);
+  display: flex;
+  align-items: center;
+  gap: 0.6rem;
+}
+.version-badge {
+  font-family: ui-monospace, monospace;
+  font-size: 0.8rem;
+  padding: 0.15rem 0.5rem;
+  background: var(--color-bg-secondary);
+  border: 1px solid var(--color-border);
+  border-radius: 4px;
+  color: var(--color-text-muted);
+}
+
 /* ── Groups tab ──────────────────────────────────────────────── */
 .btn-primary {
   padding: 0.4rem 0.9rem;