feat(character-banner): 캐릭터 배너 등록 다이얼로그

- 캐릭터 검색 결과가 없으면 '검색결과가 없습니다.'라고 안내

src/views/Chat/CharacterBanner.vue

@@ -174,6 +174,16 @@
                 </v-list>
               </v-col>
             </v-row>
+            <v-row v-if="searchPerformed && searchResults.length === 0">
+              <v-col cols="12">
+                <v-alert
+                  type="info"
+                  outlined
+                >
+                  검색결과가 없습니다.
+                </v-alert>
+              </v-col>
+            </v-row>
             <v-row v-if="selectedCharacter">
               <v-col cols="12">
                 <v-alert
@@ -284,6 +294,7 @@ export default {
       selectedCharacter: null,
       searchKeyword: '',
       searchResults: [],
+      searchPerformed: false,
       previewImage: null,
       bannerForm: {
         image: null,
@@ -383,6 +394,7 @@ export default {
       this.previewImage = null;
       this.searchKeyword = '';
       this.searchResults = [];
+      this.searchPerformed = false;
       this.showDialog = true;
     },
 
@@ -403,6 +415,7 @@ export default {
       this.previewImage = null;
       this.searchKeyword = '';
       this.searchResults = [];
+      this.searchPerformed = false;
       this.showDialog = true;
     },
 
@@ -418,6 +431,7 @@ export default {
       this.previewImage = null;
       this.searchKeyword = '';
       this.searchResults = [];
+      this.searchPerformed = false;
     },
 
     confirmDelete(banner) {
@@ -446,6 +460,7 @@ export default {
 
         if (response && response.data) {
           this.searchResults = response.data.content || [];
+          this.searchPerformed = true;
         }
       } catch (error) {
         console.error('캐릭터 검색 오류:', error);