Fix NAND archive path resolution and OLED temp space checks

[denchik28]

Summary

This PR fixes two issues in nandfixpro.py:

1. NAND archive resolution
   In several flows, archive paths were hardcoded to script_dir/lib/NAND, which could fail depending on runtime context.
   The code now resolves archives consistently via partitions_folder from Settings, with a stable app-directory fallback.

2. Temp disk space checks for OLED / 64GB NAND
   Space checks were previously static and could underestimate required free space for OLED-sized NAND.
   The required free temp space is now dynamic:

   • 32GB NAND class -> 64GB required
   • 64GB NAND class (OLED) -> 128GB required

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What changed

• Added helper methods:
  • _get_app_base_dir()
  • _get_partitions_folder()
  • _estimate_nand_size_gb()
  • _required_temp_space_gb()
• Replaced hardcoded lib/NAND path usage in:
  • Advanced USER fix flow
  • Level 2 rebuild flow
  • Level 3 donor NAND preparation + partition extraction flow
• Updated Level 2/3 to run disk-space check using dynamic required space based on detected NAND size.
• Added explicit user-facing error when partition archives folder cannot be resolved.

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Validation

• python3 -m py_compile nandfixpro.py passes.