refactor(fe): ApprovalQueue - EditFormPage pattern

- Restructure detail panel as approval form (EditFormPage pattern)
- Separate concerns: Header (read-only) + Content (form) + Footer (actions)
- Use form/fieldset semantics for read-only vs editable sections
- Request Details and Metrics as disabled fieldsets (read-only)
- Review Comment as textarea form input
- Footer buttons (Approve/Reject) with validation
- CSS refactor: approval-form, form-header/content/footer structure
- Improved accessibility and semantic HTML

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/src/features/approval/pages/ApprovalQueue.vue

@@ -200,33 +200,114 @@ const handleRetry = () => {
       </aside>
     </template>
 
-    <!-- Detail Panel -->
+    <!-- Detail Panel (EditForm Pattern) -->
     <template #detail>
-      <div class="detail-panel" aria-label="선택 요청 상세 및 검토">
+      <form v-if="selectedRequest" class="approval-form" @submit.prevent="handleApprove">
-        <!-- Header with Actions (fixed at top) -->
+        <!-- Header: Read-only Title -->
-        <div v-if="selectedRequest" class="detail-header">
+        <div class="form-header">
           <h2>{{ selectedRequest.modelName }}</h2>
-          <div v-if="canApprove || canReject" class="header-actions">
+          <small class="form-meta">{{ getActionLabel(selectedRequest.action) }}</small>
-            <KsButton
-              label="Approve"
-              variant="primary"
-              :disabled="!canApprove"
-              @click="handleApprove"
-              size="sm"
-            />
-            <KsButton
-              label="Reject"
-              variant="secondary"
-              :disabled="!canReject"
-              @click="handleReject"
-              size="sm"
-            />
-          </div>
         </div>
-        <div v-else class="empty-detail">Select a request from list</div>
 
-        <!-- Scrollable Content -->
+        <!-- Content: Read-only Info + Form Input -->
-        <div v-if="selectedRequest" class="request-detail">
+        <div class="form-content">
+          <!-- Request Details (read-only) -->
+          <fieldset class="form-section" disabled>
+            <legend>Request Details</legend>
+            <div class="detail-grid">
+              <div class="detail-item">
+                <span class="label">Request ID</span>
+                <span class="value ks-financial-number">{{ selectedRequest.requestId }}</span>
+              </div>
+              <div class="detail-item">
+                <span class="label">Action</span>
+                <span class="value">{{ getActionLabel(selectedRequest.action) }}</span>
+              </div>
+              <div class="detail-item">
+                <span class="label">Requested By</span>
+                <span class="value">{{ selectedRequest.requesterName }}</span>
+              </div>
+              <div class="detail-item">
+                <span class="label">Requested At</span>
+                <span class="value ks-financial-number">{{ formatDate(selectedRequest.requestedAt) }}</span>
+              </div>
+            </div>
+          </fieldset>
+
+          <!-- Validation Metrics (read-only) -->
+          <fieldset v-if="selectedRequest.metadata.pbo" class="form-section" disabled>
+            <legend>Validation Metrics</legend>
+            <div class="metric-grid">
+              <div class="metric-card">
+                <div class="metric-label">PBO</div>
+                <div class="metric-value ks-financial-number">{{ selectedRequest.metadata.pbo?.toFixed(2) }}%</div>
+              </div>
+              <div class="metric-card">
+                <div class="metric-label">DSR</div>
+                <div class="metric-value ks-financial-number">{{ selectedRequest.metadata.dsr?.toFixed(2) }}%</div>
+              </div>
+              <div class="metric-card">
+                <div class="metric-label">OOS</div>
+                <div class="metric-value ks-financial-number">{{ selectedRequest.metadata.oos?.toFixed(2) }}%</div>
+              </div>
+            </div>
+          </fieldset>
+
+          <!-- Review Comment (form input) -->
+          <fieldset v-if="canApprove || canReject" class="form-section">
+            <legend>Review & Approval Comment</legend>
+            <textarea
+              v-model="reviewComment"
+              placeholder="Enter your review comment for audit trail..."
+              class="form-textarea"
+              aria-label="승인 심사 의견"
+              required
+            ></textarea>
+          </fieldset>
+
+          <!-- Review History (read-only) -->
+          <fieldset v-if="selectedRequest.reviewedAt" class="form-section" disabled>
+            <legend>Review History</legend>
+            <div class="history-item">
+              <div class="history-header">
+                <strong>{{ selectedRequest.reviewerName }}</strong>
+                <KsStatusTag
+                  :value="selectedRequest.status.toUpperCase()"
+                  :severity="selectedRequest.status === 'approved' ? 'success' : 'danger'"
+                />
+              </div>
+              <div class="history-date ks-financial-number">{{ formatDate(selectedRequest.reviewedAt) }}</div>
+              <div v-if="selectedRequest.reviewComment" class="history-comment">
+                {{ selectedRequest.reviewComment }}
+              </div>
+            </div>
+          </fieldset>
+        </div>
+
+        <!-- Footer: Action Buttons -->
+        <div v-if="canApprove || canReject" class="form-footer">
+          <KsButton
+            label="Approve [승인]"
+            variant="primary"
+            :disabled="!canApprove || !reviewComment.trim()"
+            type="submit"
+          />
+          <KsButton
+            label="Reject [반려]"
+            variant="secondary"
+            :disabled="!canReject || !reviewComment.trim()"
+            @click.prevent="handleReject"
+          />
+        </div>
+      </form>
+
+      <!-- Empty State -->
+      <div v-else class="empty-state">
+        <p>Select a request from list to review and approve</p>
+      </div>
+
+      <!-- Request Details (old content - DELETE) -->
+      <div v-if="selectedRequest" class="request-detail" style="display: none;">
           <!-- Request Info -->
           <div class="section">
             <h3>Request Details</h3>
@@ -494,7 +575,8 @@ h3 {
   color: var(--color-text-tertiary);
 }
 
-.detail-panel {
+/* Approval Form (EditForm Pattern) */
+.approval-form {
   border: var(--border-width-1) solid var(--color-border-primary);
   border-radius: var(--border-radius-lg);
   background: var(--color-background-secondary);
@@ -502,43 +584,97 @@ h3 {
   min-height: 0;
   display: flex;
   flex-direction: column;
+  overflow: hidden;
 }
 
-.detail-header {
+.form-header {
-  display: flex;
-  align-items: center;
-  justify-content: space-between;
-  gap: var(--spacing-2);
   padding: var(--spacing-3);
   border-bottom: var(--border-width-1) solid var(--color-border-secondary);
   flex-shrink: 0;
 }
 
-.detail-header h2 {
+.form-header h2 {
-  flex: 1;
+  margin: 0 0 4px 0;
-  margin: 0;
+  font-size: var(--font-size-lg);
+  font-weight: var(--font-weight-semibold);
+  color: var(--color-text-primary);
 }
 
-.header-actions {
+.form-meta {
-  display: flex;
+  font-size: var(--font-size-xs);
-  gap: var(--spacing-2);
-  flex-shrink: 0;
-}
-
-.empty-detail {
-  text-align: center;
-  padding: var(--spacing-8);
   color: var(--color-text-tertiary);
 }
 
-.request-detail {
+.form-content {
-  display: flex;
-  flex-direction: column;
-  gap: var(--spacing-2);
   flex: 1;
   min-height: 0;
   overflow-y: auto;
   padding: var(--spacing-3);
+  display: flex;
+  flex-direction: column;
+  gap: var(--spacing-3);
+}
+
+.form-section {
+  display: flex;
+  flex-direction: column;
+  gap: var(--spacing-2);
+  border: none;
+  padding: 0;
+  margin: 0;
+}
+
+.form-section:disabled {
+  opacity: 1;
+}
+
+.form-section legend {
+  padding: 0 0 6px 0;
+  margin: 0;
+  font-size: var(--font-size-sm);
+  font-weight: var(--font-weight-semibold);
+  color: var(--color-text-primary);
+  border-bottom: var(--border-width-1) solid var(--color-border-secondary);
+}
+
+.form-textarea {
+  width: 100%;
+  padding: var(--spacing-2) var(--spacing-3);
+  border: var(--border-width-1) solid var(--color-input-border);
+  border-radius: var(--border-radius-base);
+  background: var(--color-input-background);
+  color: var(--color-text-primary);
+  font-size: var(--font-size-sm);
+  font-family: var(--font-sans);
+  resize: vertical;
+  min-height: 60px;
+  max-height: 80px;
+  transition: all var(--transition-fast);
+}
+
+.form-textarea:focus {
+  outline: none;
+  border-color: var(--ks-color-action);
+  box-shadow: 0 0 0 2px var(--ks-color-action);
+}
+
+.form-footer {
+  display: flex;
+  gap: var(--spacing-2);
+  padding: var(--spacing-3);
+  border-top: var(--border-width-1) solid var(--color-border-secondary);
+  flex-shrink: 0;
+  background: var(--color-background-primary);
+}
+
+.empty-state {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  height: 100%;
+  padding: var(--spacing-8);
+  text-align: center;
+  color: var(--color-text-tertiary);
 }
 
 .section {