fix(ios): prevent compressVideo hang on writer failure and reject on reader failure (#5)

[thangdevalone]

Closes #5

Summary

• Checks append(...) boolean returns and writer.status in both video and audio loops.
• Cancels reader and marks inputs as finished on writer failure, guaranteeing group.leave() is called so JS promise never hangs.
• Detects reader.status == .failed and rejects with reader.error instead of succeeding with a truncated file.
• Throttles onProgress to 1% intervals to prevent flooding DispatchQueue.main.
• Initializes CIContext(options: [.cacheIntermediates: false]) to avoid memory bloat during per-frame resize.