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>

README.md

@@ -81,3 +81,8 @@ Repo-only material:
 - [`NOTEPAD.md`](NOTEPAD.md) — deferred work and findings
 - [`DESIGN.md`](DESIGN.md) — points at the workspace root's `DESIGN-GUIDELINES.md`
 - `docs/architecture/` in the sibling `docs` repo — the requirement sources
+
+## License
+
+Copyright (C) 2026 Melvin Strobl — GNU Affero General Public License v3.0 or
+later. See [LICENSE](LICENSE).