feat: FS-E strict filesystem mode - ext4 rw driver, FAT32 big-disk fix, forced re-login

- CODE/dsk/ext4.c: minimal full ext4 read/write (GPT probe, feature gate,
  extent depth 0/1 rw, block/inode alloc-free, dir insert, write-verify);
  boot selftest PASS on p2. Unsupported features panic (FS-E2x), zero fallback.
- DSK fat32 write: on-demand FAT entry RMW + chunked free-cluster scan
  (fixes "no free clusters" on 5.3G ESP); rec_len shrink offset (+4) and
  chunk alignment fixes. USER.CONF write-verify ok, firstInit flip ok.
- First-boot: wizard -> persist -> forced login (FS-E06 if skipped/failed)
  -> desktop. login.elf loaded via system/user/use fallback.
- FirstInit network page: Connect now panics NET-E01 (no wlan stack);
  Save (config only) is the only path forward.
- FirstInit/DSK fatal: ohMyLogo lotus fatal screen (NET-E01 / FS-E series).
- Boot screen: Logo.png image removed, "DESHAB P01" text centered only;
  dcp/xj logos regenerated from TEXTURES/.
- run_qemu.bat: main GPT image on SATA ide.0 (AHCI provider must see ext4).

CODE/dsk/ext4.h

@@ -0,0 +1,43 @@
+/* ext4.h — minimal full read-write ext4 driver for DSK (p2 data partition)
+ *
+ * 严格错误策略：任何错误（挂载失败/feature 不支持/IO 失败/校验不符）
+ * 一律经 fatal(sym) 整屏 panic 停机，错误码体系 FS-E1x / FS-E2x。
+ *
+ * 支持范围（mkfs.ext4 由 pack_system_image.sh 以 -O
+ * ^has_journal,^metadata_csum,^64bit,^resize_inode -b 4096 -I 256 创建）：
+ *   - 4K blocksize、inode 256B、无 journal、无 metadata_csum、无 64bit
+ *   - extent 树（depth 0/1）读写
+ *   - 块位图/inode 位图分配与回收
+ *   - 线性目录项查找/插入/扩展
+ */
+#ifndef DSK_EXT4_H
+#define DSK_EXT4_H
+
+typedef unsigned char  ext4_u8;
+typedef unsigned short ext4_u16;
+typedef unsigned int   ext4_u32;
+typedef unsigned long long ext4_u64;
+
+typedef int (*ext4_block_read_fn)(unsigned int index, ext4_u64 lba,
+                                  ext4_u32 count, void *buf);
+typedef int (*ext4_block_write_fn)(unsigned int index, ext4_u64 lba,
+                                   ext4_u32 count, const void *buf);
+
+/* 挂载 p2 ext4 分区（GPT 探测 + superblock/feature 校验）。
+ * 任何失败直接调用 fatal(sym) panic。成功返回 0。 */
+int ext4_mount(ext4_block_read_fn rd, ext4_block_write_fn wr,
+               void (*fatal)(const char *sym), void (*logl)(const char *s),
+               void (*logh)(const char *p, ext4_u64 v));
+
+/* 按路径读文件（"/system/deshab64/FUCK"），返回内部静态缓冲。
+ * 任何失败 fatal。成功返回 0 并填充 out/size。 */
+int ext4_read_file(const char *path, ext4_u8 **out, ext4_u32 *size);
+
+/* 按路径写文件（存在则覆写，不存在则创建）。
+ * 写后自动回读逐字节校验，不符 fatal。成功返回 0。 */
+int ext4_write_file(const char *path, const ext4_u8 *data, ext4_u32 size);
+
+/* 启动自检：读 /system/deshab64/FUCK + 写读校验 /dsk_ext4_rw.test。 */
+void ext4_boot_selftest(void);
+
+#endif