Add support for multiple nationalities display with flags

- Create MultipleCountryFlags component to display multiple country flags
- Support comma-separated nationality values (e.g., 'FR,MC,US')
- Update admin members page to use MultipleCountryFlags in both list and grid views
- Update board members page to display nationalities with flags
- Add nationality column to board members table
- Update member forms to support multiple nationality selection
- Display flags with slight overlap for space efficiency, expand on hover
- Maintain backward compatibility with single nationality values

🤖 Generated with [Claude Code](https://claude.ai/code)

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

pages/admin/members/index.vue

@@ -190,14 +190,12 @@
 
         <template v-slot:item.nationality="{ item }">
           <div class="d-flex align-center">
-            <CountryFlag
-              v-if="item.nationality"
-              :country-code="item.nationality"
-              :show-name="false"
+            <MultipleCountryFlags
+              :nationality="item.nationality"
+              :show-name="true"
               size="small"
-              class="mr-2"
+              fallback-text="Not specified"
             />
-            <span>{{ getCountryName(item.nationality) || 'Not specified' }}</span>
           </div>
         </template>
 
@@ -320,16 +318,13 @@
             </h3>
             
             <div class="d-flex align-center justify-center mb-3">
-              <CountryFlag
-                v-if="member.nationality"
-                :country-code="member.nationality"
-                :show-name="false"
+              <MultipleCountryFlags
+                :nationality="member.nationality"
+                :show-name="true"
                 size="small"
-                class="mr-2"
+                fallback-text="No nationality"
+                class="text-body-2 text-medium-emphasis"
               />
-              <span class="text-body-2 text-medium-emphasis">
-                {{ getCountryName(member.nationality) || 'No nationality' }}
-              </span>
             </div>
             
             <!-- Email -->