feat: auto-mount boot drive to /boot; fix FAT32 deleted entry triple fault

- Decode multiboot boot_device byte in storagemanager to identify boot device
- Add isBootDevice to TStorage_Device; propagate isBootDrive to volumes
- Create /boot VFS directory at init; mount boot volume there in auto_mount_volumes
- Fix getDirEntries skipping \-marked (deleted) FAT32 entries to prevent
  triple fault when navigating into a deleted directory via file picker

.gitignore

@@ -1,12 +1,13 @@
-*.o
-*.ppu
-*.s
-*.iso
-*.elf
-lib/
-release/
-doc/
-bin/
+/lib/*.ppu
+/lib/*.a
+/lib/*.o
+/release/*.svg
+/release/*.iso
+/bin/*.bin
+/iso/boot/asuro.bin
+/*.iso
+/*.md5
+/*.sh~
 /*.img
 src/include/asuro.pas
 localenv.json