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/plex_relay/tests/test_models.py

@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+import pytest
+
+from plex_relay.errors import RelayKeyError
+from plex_relay.models import HostKey, RelayKey, known_hosts_endpoint, parse_relay_pub
+
+PUB = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIabc relay@plex"  # keytype keydata comment
+KH = "* ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIabc"            # host keytype keydata
+EXPECT = RelayKey("ssh-ed25519", "AAAAC3NzaC1lZDI1NTE5AAAAIabc")
+
+
+def test_parse_pubkey_form():
+    assert parse_relay_pub(PUB) == EXPECT
+
+
+def test_parse_known_hosts_form():
+    assert parse_relay_pub(KH) == EXPECT
+
+
+def test_parse_skips_comments_and_blanks():
+    assert parse_relay_pub(f"# header\n\n{PUB}\n") == EXPECT
+
+
+@pytest.mark.parametrize("bad", ["ssh-ed25519 onlytwo", "aaa bbb ccc", "", "# only comment\n"])
+def test_parse_rejects_bad_payloads(bad):
+    with pytest.raises(RelayKeyError):
+        parse_relay_pub(bad)
+
+
+def test_endpoint_bracket_notation():
+    assert known_hosts_endpoint("1.2.3.4", 443) == "[1.2.3.4]:443"
+    assert known_hosts_endpoint("relay.example", 2222) == "[relay.example]:2222"
+    assert known_hosts_endpoint("relay.example", 22) == "relay.example"
+
+
+def test_endpoint_rejects_empty_host():
+    with pytest.raises(RelayKeyError):
+        known_hosts_endpoint("   ", 443)
+
+
+def test_hostkey_serialization():
+    hk = HostKey.for_endpoint("[1.2.3.4]:443", EXPECT)
+    assert hk.known_hosts_line() == "[1.2.3.4]:443 ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIabc"
+    assert hk.cache_block() == f"# [1.2.3.4]:443\n{hk.known_hosts_line()}\n"
+    assert hk.key == EXPECT