Switch mods to per-folder auto-discovery and resourcepack to single zip

- PackDefinition: replace mods[]/resourcepacks[] with modsFolder (string) + resourcepackPath (string); drop PackAsset
- Editor: replace dynamic add/remove lists with two single inputs; remove the now-dead JS for adding/removing rows
- Server: expose GET /file/mods/<folder>/index.json that returns the list of .jar names; folder name restricted to [a-zA-Z0-9_-]+
- Installer: fetch the listing JSON and download each jar from /file/mods/<folder>/<file>.jar; download the single resourcepack from /file/resourcepacks/<file>.zip directly into resourcepacks/

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

views/op/dashboard.ejs

@@ -38,7 +38,7 @@
                 <ul class="metaList">
                   <li>MC <%= item.definition.mcVersion %></li>
                   <li>플랫폼 <%= item.definition.platform.type %></li>
-                  <li>모드 <%= item.definition.mods.length %>개</li>
+                  <li>모드 폴더 <%= item.definition.modsFolder || '없음' %></li>
                 </ul>
               <% } %>
             </a>