rename: IAMROOT → SKELETONKEY across the entire project

Breaking change. Tool name, binary name, function/type names,
constant names, env vars, header guards, file paths, and GitHub
repo URL all rebrand IAMROOT → SKELETONKEY.

Changes:
  - All "IAMROOT" → "SKELETONKEY" (constants, env vars, enum
    values, docs, comments)
  - All "iamroot" → "skeletonkey" (functions, types, paths, CLI)
  - iamroot.c → skeletonkey.c
  - modules/*/iamroot_modules.{c,h} → modules/*/skeletonkey_modules.{c,h}
  - tools/iamroot-fleet-scan.sh → tools/skeletonkey-fleet-scan.sh
  - Binary "iamroot" → "skeletonkey"
  - GitHub URL KaraZajac/IAMROOT → KaraZajac/SKELETONKEY
  - .gitignore now expects build output named "skeletonkey"
  - /tmp/iamroot-* tmpfiles → /tmp/skeletonkey-*
  - Env vars IAMROOT_MODPROBE_PATH etc. → SKELETONKEY_*

New ASCII skeleton-key banner (horizontal key icon + ANSI Shadow
SKELETONKEY block letters) replaces the IAMROOT banner in
skeletonkey.c and README.md.

VERSION: 0.3.1 → 0.4.0 (breaking).

Build clean on Debian 6.12.86. `skeletonkey --version` → 0.4.0.
All 24 modules still register; no functional code changes — pure
rename + banner refresh.

modules/entrybleed_cve_2023_0458/skeletonkey_modules.h

@@ -0,0 +1,20 @@
+/*
+ * entrybleed_cve_2023_0458 — SKELETONKEY module registry hook
+ */
+
+#ifndef ENTRYBLEED_SKELETONKEY_MODULES_H
+#define ENTRYBLEED_SKELETONKEY_MODULES_H
+
+#include "../../core/module.h"
+
+extern const struct skeletonkey_module entrybleed_module;
+
+/* Library entry point for other modules that need a kbase leak.
+ * Returns the leaked kernel _text base on success, or 0 on failure
+ * (x86_64 only; ARM and other arches return 0). The optional
+ * `entry_syscall_slot_offset` is the offset from kbase to
+ * entry_SYSCALL_64's 2MiB-aligned slot. Pass 0 for a kernel-default
+ * (lts-6.12.x-style; ~0x5600000). */
+unsigned long entrybleed_leak_kbase_lib(unsigned long entry_syscall_slot_offset);
+
+#endif