fix(modpack-checker): Code review fixes — license, safety, and polish

Fixes 10 issues from full code review:
- License corrected from MIT to Commercial
- Deprecated datetime.utcnow() replaced with timezone-aware alternative
- PHP array bounds checks added for all platform API responses
- Modrinth file detection now derives project slug instead of using MC version
- validate_api_key() no longer swallows network errors
- HTTP timeouts added to all external API calls in PHP
- Empty API key rejection added to CLI
- Corrupted config now warns on stderr instead of failing silently
- Error response format made consistent across controller
- Docs updated with correct repo URL and clearer CurseForge ID instructions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

services/modpack-version-checker/setup.py

@@ -17,7 +17,7 @@ setup(
     long_description=long_description,
     long_description_content_type="text/markdown",
     url="https://firefrostgaming.com",
-    license="MIT",
+    license="Commercial",
     packages=find_packages(where="src"),
     package_dir={"": "src"},
     python_requires=">=3.9",
@@ -47,7 +47,7 @@ setup(
         "Development Status :: 5 - Production/Stable",
         "Environment :: Console",
         "Intended Audience :: System Administrators",
-        "License :: OSI Approved :: MIT License",
+        "License :: Other/Proprietary License",
         "Operating System :: OS Independent",
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.9",