feat: System Info — export full machine report as PDF

[chojuninengu]

Summary

Add an "Export Report" button to the System Info tab that generates a clean,
professionally formatted PDF containing the machine's full specs, battery health,
disk usage, and a timestamp — ready to share when buying or selling a machine.

Why

This completes the flagship use case Sysora was designed for from day one.
Right now users have to screenshot the System Info tab. A one-click PDF export
makes Sysora the go-to tool for hardware transactions and IT audits.

Scope

Rust backend

• Add export_report(output_path: String) -> Result<(), String> Tauri command
• Add printpdf crate to Cargo.toml:

  printpdf = "0.7"

• Gather all data in one shot:
  • System: OS, kernel, hostname, uptime, CPU brand + cores
  • Memory: total, used, free, swap
  • Disks: all mounted disks with usage
  • Battery: health %, design capacity, current capacity, cycle count
  • Network: interfaces and IP addresses
  • Report generated timestamp
• Generate a clean single-page PDF with:
  • Sysora logo/name header
  • Sections for each category
  • Color-coded health indicators (green/amber/red)
  • Footer with generation timestamp and hostname
• Save to user's chosen path via Tauri file dialog

Frontend

• Add Export Report button to System Info tab header
• Open native save dialog (using @tauri-apps/plugin-dialog) for output path
• Show loading spinner while generating
• Show success toast with file path on completion
• Show error toast if generation fails

Acceptance criteria

• PDF generates successfully on Ubuntu, macOS, and Windows
• PDF contains: OS info, CPU, RAM, disk usage, battery health, network interfaces
• File saves to user-chosen location
• PDF is clean and readable — suitable to send to a buyer or IT department
• Generation completes in under 3 seconds