fix: Zenodo + CITATION metadata — bump to v0.3.1, add date-released

[Zer0pa-Architect-Prime]

What

Zenodo/citation metadata hygiene for the v0.3.1 release (PyPI live since 2026-04-25).

File	Change
CITATION.cff	version: 0.3.0 → 0.3.1; add date-released: "2026-04-25"
.zenodo.json	add "version": "0.3.1" field

Why

• CITATION.cff was not bumped when v0.3.1 shipped to PyPI; Zenodo auto-capture and academic citation tools would have cited the wrong version.
• .zenodo.json had no version field; Zenodo would infer it from the tag name but explicit is safer.
• No other content changed — no code, no workflow, no README, no redaction-relevant surface.

Checks

• No private/operator names introduced.
• No ZPE-IMC active framing.
• No PyPI tag pushed.
• License field unchanged (LicenseRef-Zer0pa-SAL-7.0).

Remaining open items (operator decision needed, not in this PR)

• SAL v7.0 vs v7.1 version conflict in README (badge + Repo Identity vs Quick Start prose) — flagged in Phase 1 STATE report.
• ## Provenance section absent from README (§3.3 compliance gap).
• commit_sha in README ## Repo Identity is stale (c5e8bf11a1c1 vs live HEAD).