⚡ Bolt: Cache Printify blueprint variants to prevent N+1 queries

[merg357]

💡 What: Added @functools.lru_cache(maxsize=None) to get_variants() in printify_manager.py and cast the result to an immutable tuple.
🎯 Why: The cmd_create loop calls get_variants() for the same blueprints repeatedly. This eliminates redundant API requests (N+1 queries). Returning a tuple prevents unintended downstream state mutation while remaining compatible with json.dumps().
📊 Impact: Eliminates N+1 redundant network requests, speeding up the product creation loop significantly.
🔬 Measurement: Run python3 printify_manager.py run and observe fewer total API calls and faster creation times.

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PR created automatically by Jules for task 17004187473736578026 started by @merg357

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