Relicense under GPL-3.0-or-later

Replace MIT with the full GNU GPLv3 text, update license metadata in
pyproject.toml (+ trove classifiers) and PKGBUILD, and add
SPDX-License-Identifier headers to all Python modules and shell scripts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

pyproject.toml

@@ -8,9 +8,15 @@ version = "0.2.0"
 description = "Host intrusion-detection daemon — signature-based detection of reverse shells, LD_PRELOAD rootkits, fileless malware, and persistence tampering"
 readme = "README.md"
 requires-python = ">=3.11"
-license = { text = "MIT" }
+license = { text = "GPL-3.0-or-later" }
 authors = [{ name = "Enodia" }]
 keywords = ["security", "ids", "hids", "detection", "linux", "forensics"]
+classifiers = [
+    "License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)",
+    "Operating System :: POSIX :: Linux",
+    "Programming Language :: Python :: 3",
+    "Topic :: Security",
+]
 # Zero runtime dependencies — stdlib only, by design (a system security
 # daemon should not pull in a dependency tree it has to trust and update).
 dependencies = []