feat(pc): virtual NAND simulation for little_flash

[wendal]

Summary

• Add PC virtual SPI NAND backend for little_flash (JEDEC/status/read/prog/erase)
• Add deterministic bad-block simulation and fast/dev/realistic timing profiles
• Add lf_nand_basic testcase covering RED/GREEN, /nand mount, and /lfs2 coexistence

Test Plan

• cd bsp\pc && cmd /c build_windows_32bit_msvc.bat
• LF_NAND_TEST_MODE=GREEN, LUAT_PC_NAND_PROFILE=fast: run lf_nand_basic
• LF_NAND_TEST_MODE=RED: run lf_nand_basic (expected init-fail path)

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[CLAassistant]

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0 out of 10 committers have signed the CLA.

❌ shuaizenge
❌ jiangfang001
❌ Jiangqian
❌ shihao-w
❌ PeakRacing
❌ chao-HHH-lang
❌ li3211
❌ allewalker
❌ wendal
❌ mengyang-GitHub

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[sonarqubecloud]

Quality Gate passed

Issues
22 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud