feat: Flash-HAL-Interface und Settings-Store mit A/B-Slots

Implementiert:
- Flash HAL (nl_flash_read/write/erase_sector) Interfaces
- Flash Layout mit A/B-Settings Slots und weiteren Regions
- Test-Fake für Flash mit Fehlerinjection (Stromausfall-Simulation)
- Settings-Store mit CRC32 Recovery und Slot-Alternierung
- Vollständige Test-Suite mit Corruption/Power-Loss-Tests

test/fake_flash.h

@@ -0,0 +1,19 @@
+#ifndef FAKE_FLASH_H
+#define FAKE_FLASH_H
+
+#include <stdint.h>
+
+#include "config/nl_flash.h"
+
+#define FAKE_FLASH_SECTORS 8u
+#define FAKE_FLASH_SIZE (FAKE_FLASH_SECTORS * NL_FLASH_SECTOR_SIZE)
+
+extern uint8_t fake_flash_mem[FAKE_FLASH_SIZE];
+extern unsigned fake_flash_erases[FAKE_FLASH_SECTORS];
+extern unsigned fake_flash_dirty_writes; /* writes onto non-erased bytes (store bug) */
+
+void fake_flash_reset(void);
+/* Simulate power loss: after `bytes` more written bytes every write/erase fails. -1 = never. */
+void fake_flash_fail_after(long bytes);
+
+#endif