feat: overall completion bar on project cards; auto-collapse done milestones

ProjectListView: add an overall task completion bar above the per-milestone
bars showing the percentage of all project tasks that are done.

ProjectView: milestones where every task is complete now start collapsed
by default, keeping the view clean for projects with many finished stages.

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

frontend/src/views/ProjectView.vue

@@ -118,6 +118,14 @@ function toggleMilestoneCollapse(id: number) {
   }
 }
 
+function autoCollapseCompleted(msList: Milestone[]) {
+  for (const ms of msList) {
+    if (ms.total > 0 && ms.completed === ms.total) {
+      collapsedMilestones.value.add(ms.id);
+    }
+  }
+}
+
 async function loadProject() {
   loading.value = true;
   error.value = null;
@@ -130,6 +138,7 @@ async function loadProject() {
     editStatus.value = data.status;
     editDirty.value = false;
     milestones.value = data.summary?.milestone_summary ?? [];
+    autoCollapseCompleted(milestones.value);
   } catch {
     error.value = "Failed to load project.";
   } finally {
@@ -143,6 +152,7 @@ async function loadMilestones() {
       `/api/projects/${projectId.value}/milestones`
     );
     milestones.value = data.milestones;
+    autoCollapseCompleted(milestones.value);
   } catch {
     // silent
   }