Replace patchelf crack with Freeloader LD_PRELOAD approach

- Multi-stage Dockerfile: discover patterns from PMS binary (capstone),
  compile .so with zig (musl), layer onto lscr.io/linuxserver/plex
- Uses LD_PRELOAD instead of patchelf (which corrupts Plex's musl loader)
- Auto-discovery: broad structural patterns with string-anchored fallback
  (//feature) and relationship-based fallback (BITSET_REF within BS_INIT)
- hook.cpp uses __has_include for generated patterns with hardcoded fallbacks
- Custom wrapper.sh (no traffic_logger preload)
- Vendored Freeloader source (github.com/authrequest/Freeloader, AGPL-3.0)
- Removed stale plexmediaserver_crack.so binary
- Supports Plex 1.43.3+ (verified against 1.43.2 and 1.43.3)

Freeloader/src/main.cpp

@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+#include "hook.hpp"
+#include "webhook_handler.hpp"
+
+#include <stdlib.h>
+
+// ---------------------------------------------------------------------------
+// The old constructor called hook() synchronously, but under musl the
+// LD_PRELOAD library's constructor runs *before* the main binary is loaded
+// → dl_iterate_phdr returned 0 callbacks, and /proc/self/maps doesn't yet
+// contain the PMS text segment → hook() = no-op.
+//
+// We now combine two strategies:
+//
+//   1. Try hook() immediately (best-effort – will fail if the binary
+//      isn't mapped yet, which is both harmless and informative).
+//
+//   2. Override a function that PMS calls during runtime startup but well
+//      after all libraries are loaded.  When that override first fires, it
+//      calls hook() and then passes through to the real function.
+//
+// Strategy 2 uses a trigger that's guaranteed to fire during normal PMS
+// operation but AFTER boost::uuids, epoll, and the HTTP server are all
+// initialised.  We override `epoll_create1` (called by the event loop)
+// rather than `bind` (which the musl dynamic linker may reference during
+// loading, causing boost UUID crashes).
+//
+// Both strategies are idempotent: hook() is guarded by the TextSpan check
+// on the inside (returns immediately if text range not found / hooks
+// already set), and the deferred trigger is a one-shot flag.
+// ---------------------------------------------------------------------------
+
+static int g_hooks_attempted = 0;
+
+// ---- deferred trigger: epoll_create1 override ----
+//
+// PMS uses epoll for its event loop.  The first epoll_create1 call happens
+// during server initialisation, long after the main binary is fully mapped.
+// This is a safer trigger than bind (which libc's NSS/resolver may call
+// during dlopen, triggering boost::uuids crashes).
+
+#include <sys/epoll.h>
+#include <dlfcn.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+
+typedef int (*RealEpollFn)(int);
+
+static int g_epoll_triggered = 0;
+
+int epoll_create1(int flags)
+{
+    if(!g_epoll_triggered)
+    {
+        g_epoll_triggered = 1;
+        hook();
+
+        RealEpollFn real = (RealEpollFn)dlsym(RTLD_NEXT, "epoll_create1");
+        if(real)
+            return real(flags);
+        return syscall(SYS_epoll_create1, flags);
+    }
+
+    RealEpollFn real = (RealEpollFn)dlsym(RTLD_NEXT, "epoll_create1");
+    if(real)
+        return real(flags);
+    return syscall(SYS_epoll_create1, flags);
+}
+
+__attribute__((constructor)) void init_so()
+{
+    // This library is LD_PRELOADed into the (musl) "Plex Media Server" process.
+    // Plex later spawns glibc /bin/sh helpers (Plex Tuner Service, Plex Script
+    // Host, transcoders) which would inherit LD_PRELOAD and fail to load this
+    // musl .so ("/bin/sh: error while loading shared libraries"). The constructor
+    // runs before main() and before any child is spawned, so clearing LD_PRELOAD
+    // here scopes the preload to this process only.
+    unsetenv("LD_PRELOAD");
+
+    // Socket hooks in webhook_handler.cpp are active as soon as the library is
+    // preloaded. Resolve their real libc targets before PMS startup code reads
+    // from /dev/urandom; otherwise our read() interposer would fail early reads.
+    webhook_handler_init();
+
+    // Strategy 1: skipped — hook() will be triggered by the first
+    // epoll_create1 call, which happens during PMS's event loop init
+    // after everything is loaded.
+}