License the workspace under AGPL-3.0-or-later

Replace the empty LICENSE placeholders with the verbatim GNU AGPL v3 text,
fix the invalid "AGPLv3" SPDX string in the package metadata, and name
Melvin Strobl as the copyright holder wherever the old footers said
"Fluksio ... all rights reserved".

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

worker/pyproject.toml

@@ -3,6 +3,8 @@ name = "fluksio-worker"
 version = "0.1.0"
 description = "Runs Fluksio nodes on a machine the engine cannot reach"
 readme = "README.md"
+license = "AGPL-3.0-or-later"
+license-files = ["LICENSE"]
 requires-python = ">=3.10"
 authors = [{ name = "Fluksio", email = "stroblme@posteo.de" }]
 keywords = ["automation", "workflow", "distributed", "worker", "gpu"]