Add disk-backed storage for large session bodies

[NghiaTranUIT]

Summary

• Store large decoded request and response bodies on disk instead of retaining them in memory
• Keep small bodies inline for compatibility (<=512Kb), and resolve body data lazily when needed
• Stream body search and preview paths so Raw/Body/filter flows still work on large sessions
• Clean up body storage on session clear
• Add focused unit tests for storage, accumulation, and reading behavior
• Verify all debugging tools are still working with current Unit Tests

Testing

• Ran the targeted xcodebuild test scope only for body storage, preview, raw rendering, filtering, compression, import/export, and HAR coverage
• Added new unit tests for BodyStorageService, BodyAccumulator, and BodyReader
• Result: targeted ProxymanCore tests passed