style: 固定 CellData 映射基础区和添加按钮

frontend/src/components/SettingsPanel.vue

@@ -774,7 +774,9 @@
                 <n-button size="small" @click="addCellDataMappingField(sourceIndex)">添加字段</n-button>
               </div>
             </div>
-            <n-button size="small" @click="addCellDataMappingSource">添加来源</n-button>
+            <div class="cell-data-mapping-actions">
+              <n-button size="small" @click="addCellDataMappingSource">添加来源</n-button>
+            </div>
           </div>
         </section>
       </div>

frontend/src/styles.css

@@ -1640,16 +1640,24 @@ select {
 }
 
 .cell-data-settings-body {
-  display: grid;
+  display: flex;
+  height: min(68vh, 680px);
+  min-height: 0;
+  flex-direction: column;
   gap: 14px;
-  max-height: 68vh;
-  overflow-y: auto;
   padding-right: 4px;
+  overflow: hidden;
 }
 
 .cell-data-settings-section {
   display: grid;
+  flex: 0 0 auto;
   gap: 8px;
+  min-height: 0;
+}
+
+.cell-data-settings-section:last-child {
+  flex: 1 1 auto;
 }
 
 .cell-data-section-title {
@@ -1668,12 +1676,16 @@ select {
 }
 
 .cell-data-mapping-form,
-.cell-data-source-list,
 .cell-data-source-card {
   display: grid;
   gap: 10px;
 }
 
+.cell-data-mapping-form {
+  min-height: 0;
+  grid-template-rows: auto minmax(0, 1fr) auto;
+}
+
 .cell-data-mapping-key {
   display: grid;
   grid-template-columns: minmax(140px, 0.8fr) minmax(120px, 0.6fr) minmax(240px, 1.4fr);
@@ -1687,6 +1699,19 @@ select {
   border-radius: var(--td-radius-default);
 }
 
+.cell-data-source-list {
+  display: grid;
+  gap: 10px;
+  min-height: 0;
+  overflow-y: auto;
+  padding-right: 4px;
+}
+
+.cell-data-mapping-actions {
+  display: flex;
+  justify-content: flex-start;
+}
+
 .cell-data-source-header,
 .cell-data-source-meta,
 .cell-data-field-row {