Fix IGDB result selection: use DOM data attributes + pass igdb_id to backend

Two issues fixed:

1. Frontend closure bug: IGDB result buttons used Svelte {#each} closure
   with onclick={() => doUpload(result.name)}. When clicking the 3rd
   result, the 1st result's handler sometimes fired. Fixed by reading
   data-name from e.currentTarget.dataset instead of JS closure.

2. Backend scrape mismatch: when user selected 'Blood' from IGDB
   results, backend's autoScrape searched for 'Blood' and could match
   'Captain Blood' first (alphabetical), overwriting metadata.
   Now passes igdb_id along with title so backend uses the EXACT
   IGDB entry the user selected via applyIgdbId() instead of
   auto-searching.

frontend/src/pages/Library.svelte

@@ -82,12 +82,12 @@
     manualSearched = false;
   }
 
-  async function doUpload(title) {
+  async function doUpload(title, igdbId) {
     if (!pendingFile) return;
     uploading = true;
     uploadError = "";
     try {
-      await uploadGame(pendingFile, title || undefined);
+      await uploadGame(pendingFile, title || undefined, igdbId);
       cancelUpload();
       await loadGames();
     } catch (err) {
@@ -139,10 +139,12 @@
           {:else if igdbResults !== null && igdbResults.length > 0}
             <p class="match-label">Select a match or enter a custom title:</p>
             <div class="upload-igdb-results">
-              {#each igdbResults as result (result.igdb_id)}
+              {#each igdbResults as result}
                 <button
                   class="igdb-result"
-                  onclick={() => doUpload(result.name)}
+                  data-name={result.name}
+                  data-igdb-id={result.igdb_id}
+                  onclick={(e) => doUpload(e.currentTarget.dataset.name, Number(e.currentTarget.dataset.igdbId))}
                   disabled={uploading}
                 >
                   {#if result.cover_url}