feat(project): 담당자는 아이디만 표기 + 구글 머티리얼 아이콘

담당자 표시를 이메일 아이디(@ 앞)로 통일. 아바타를 letter 원형에서
구글 Material Symbols account_circle 아이콘으로 교체(멤버 목록·보드 카드·
모달 선택지·리스트 뷰).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/static/project.js

@@ -204,7 +204,10 @@
         (t.priority && t.priority !== "normal"
           ? '<span class="pj-pri pj-pri-' + t.priority + '">' + (priorityLabels[t.priority] || t.priority) + "</span>"
           : "") +
-        (t.assignee_email ? '<span class="pj-avatar pj-avatar-sm">' + escapeHtml((t.assignee_name || t.assignee_email)[0].toUpperCase()) + "</span>" : "") +
+        (t.assignee_email
+          ? '<span class="pj-assignee"><span class="material-symbols-outlined pj-gicon pj-gicon-sm">account_circle</span>' +
+            escapeHtml(idOf(t.assignee_email)) + "</span>"
+          : "") +
         (t.due_date ? '<span class="pj-card-due">' + t.due_date + "</span>" : "") +
         "</div>";
       card.addEventListener("click", function () { if (canManage) openTaskModal(t); });
@@ -244,7 +247,7 @@
         if (t.completed_at) tr.className = "is-done";
         tr.innerHTML =
           "<td>" + escapeHtml(t.title) + "</td>" +
-          "<td>" + escapeHtml(t.assignee_name || t.assignee_email || "-") + "</td>" +
+          "<td>" + (t.assignee_email ? escapeHtml(idOf(t.assignee_email)) : "-") + "</td>" +
           "<td>" + escapeHtml(t.stage_name || "-") + "</td>" +
           "<td>" + (priorityLabels[t.priority] || t.priority || "-") + "</td>" +
           "<td>" + (t.start_date || "-") + "</td>" +
@@ -367,6 +370,10 @@
     wireCalendar();
   }
 
+  function idOf(email) {
+    return String(email == null ? "" : email).split("@")[0];
+  }
+
   function escapeHtml(s) {
     return String(s == null ? "" : s)
       .replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;")