chore: relicense to Apache-2.0

[simontaurus]

Relicense from AGPL-3.0 to Apache-2.0.

Changes

• LICENSE: full Apache License 2.0 text
• NOTICE: copyright and year range, per Apache section 4(d)
• pyproject.toml: license set to Apache-2.0

Rationale

• The AGPL network clause (section 13) obliges anyone operating the software as a service to publish their full source, which industry partners' legal reviews routinely reject.
• Apache section 3 grants an explicit, irrevocable patent license covering claims necessarily infringed by each contribution, and terminates it for anyone bringing patent litigation over the work.
• Apache section 5 places inbound contributions under the project license by default, removing the need for a separate CLA.
• Apache section 6 reserves trademark rights explicitly.

Blocked pending contributor consent

Relicensing requires agreement from every holder of surviving copyrightable expression. Line counts are from git blame against the current tip, so they exclude contributions already rewritten away. They indicate rewrite cost, not voting weight: each holder can withhold consent independently regardless of size.

contributor	surviving lines
Lukas Gold	15,287
Andreas Räder	6,266
Matthias Popp	145

Do not merge until each has agreed in writing. Consent will be recorded in this PR.

[github-actions]

Release preview

No version bump from the current commits (stays at v2.3.2). Use conventional commit types (feat, fix, ...) to trigger a release.

Changelog preview (truncated)

_{Preview via python-semantic-release and conventional commits.}

[MatPoppFHG]

I agree with the rationale behind the license change.

[LukasGold]

I agree with the relicensing to Apache License 2.0