v0.8.0 - Removed Calamine

What's New in v0.8.0:

🚫 Removed Calamine - Eliminated calamine dependency completely, now 100% custom implementation
🎯 Constant Memory Streaming - Read ANY file size with only 10-12 MB RAM (tested with 1GB+ files!)
⚡ 104x Memory Reduction - 1.2GB XML → 11.6 MB RAM (vs 1204 MB with calamine)
🚀 Faster Performance - Write: 106-118K rows/sec (+70%!), Read: 50-60K rows/sec
📊 Multi-sheet Support - Full workbook.xml parsing with sheet_names() and rows_by_index()
🌍 Unicode Support - Proper handling of non-ASCII sheet names and special characters
🔧 Custom XML Parser - Chunked reading (128 KB buffers) with smart tag boundary detection
🐳 Production Ready - Process multi-GB Excel files in tiny 256 MB Kubernetes pods