fix(05-jamtrack): pass mixdown ID and package attributes to enqueue endpoint

Backend expects:
- id: mixdown ID (not package ID)
- file_type, encrypt_type, sample_rate: package attributes

The controller finds or creates the package based on these attributes.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

jam-ui/src/store/features/mediaSlice.js

@@ -137,9 +137,15 @@ export const downloadJamTrack = createAsyncThunk(
       }));
 
       // Enqueue mixdown for server-side packaging
-      console.log(`[JamTrack] Enqueueing package ${packageId} for packaging`);
+      // Backend expects mixdown ID + package attributes, not package ID
+      console.log(`[JamTrack] Enqueueing mixdown ${mixdownId} for packaging (file_type: ${compatiblePackage.file_type}, encrypt_type: ${compatiblePackage.encrypt_type}, sample_rate: ${sampleRate})`);
       try {
-        await enqueueMixdown({ id: packageId });
+        await enqueueMixdown({
+          id: mixdownId, // mixdown ID, not package ID
+          file_type: compatiblePackage.file_type,
+          encrypt_type: compatiblePackage.encrypt_type,
+          sample_rate: sampleRate
+        });
       } catch (err) {
         console.error('[JamTrack] Failed to enqueue mixdown:', err);
         throw new Error(`Failed to start packaging: ${err.message}`);