⚡ Bolt: [performance improvement] Replace Array.from with for...of in builder

[subsubl]

💡 What: Replaced the use of Array.from(filesMap.value.entries()).find(...) with for...of loops in validateFiles and packApp inside pages/builder.vue.

🎯 Why: Using Array.from() to convert an entire Map (which could contain hundreds or thousands of files) into an array just to search for a single element is highly inefficient. It triggers an unnecessary O(N) array allocation and adds pressure to the garbage collector.

📊 Impact: This change speeds up the validation and packing steps by completely avoiding the intermediate array allocation. Time complexity of the search is improved since it can early return (break) without converting the entire map first.

🔬 Measurement: Run pnpm build to verify the build completes successfully. Profile the Mini App Packer (/builder) by uploading a large app directory and measuring the heap memory usage during validation and packing.

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PR created automatically by Jules for task 1509960646220199887 started by @subsubl

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