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.c

@@ -0,0 +1,60 @@
+#include "fake_flash.h"
+
+#include <string.h>
+
+uint8_t fake_flash_mem[FAKE_FLASH_SIZE];
+unsigned fake_flash_erases[FAKE_FLASH_SECTORS];
+unsigned fake_flash_dirty_writes;
+static long s_fail_after = -1;
+
+void fake_flash_reset(void)
+{
+    memset(fake_flash_mem, 0xFF, sizeof fake_flash_mem);
+    memset(fake_flash_erases, 0, sizeof fake_flash_erases);
+    fake_flash_dirty_writes = 0;
+    s_fail_after = -1;
+}
+
+void fake_flash_fail_after(long bytes)
+{
+    s_fail_after = bytes;
+}
+
+int nl_flash_read(uint32_t addr, void *buf, uint32_t len)
+{
+    if (addr + len > FAKE_FLASH_SIZE)
+        return -1;
+    memcpy(buf, &fake_flash_mem[addr], len);
+    return 0;
+}
+
+int nl_flash_write(uint32_t addr, const void *buf, uint32_t len)
+{
+    const uint8_t *p = (const uint8_t *)buf;
+    if (addr + len > FAKE_FLASH_SIZE)
+        return -1;
+    for (uint32_t i = 0; i < len; i++) {
+        if (s_fail_after == 0)
+            return -1;
+        if (s_fail_after > 0)
+            s_fail_after--;
+        if (fake_flash_mem[addr + i] != 0xFF)
+            fake_flash_dirty_writes++;
+        fake_flash_mem[addr + i] &= p[i]; /* NOR: bits only go from 1 to 0 */
+    }
+    return 0;
+}
+
+int nl_flash_erase_sector(uint32_t addr)
+{
+    if (addr % NL_FLASH_SECTOR_SIZE || addr >= FAKE_FLASH_SIZE || s_fail_after == 0)
+        return -1;
+    memset(&fake_flash_mem[addr], 0xFF, NL_FLASH_SECTOR_SIZE);
+    fake_flash_erases[addr / NL_FLASH_SECTOR_SIZE]++;
+    return 0;
+}
+
+uint32_t nl_flash_region_base(void)
+{
+    return 0;
+}