[dzdidi]

Summary

Adds signed BTC-only provider-v2 APIs for Locks payment-only policies:

• POST /v2/invoices and POST /v2/invoices/status
• exact create replay and cross-version invoice identity
• authoritative invoice and payment deadlines
• atomic encrypted intent/outbox persistence
• immutable first-threshold payment evidence plus mutable current observation
• closed persisted provider-v2 status
• migration 0024_provider_v2_contract.sql
• explicit signed wire vectors for absent and populated status samples

This is additive. Existing v1 behavior remains unchanged. No dependency, generated-binding, or version changes are included.

Independent exact-SHA review

Internal independent review task t_9179f94c approved unchanged commit d98f3e93fa02281d6df0c888250f8abd002d9d1a (tree 05a6b7503281bb129dce36beb7a298ce4b29e3ee). Contract attachment SHA-256: 8cd97bbe1b8cce8d6f2c35b7653e01b04b2ca551d9d8bef3daa6dfeb1f5c36d6.

Review verification:

• PostgreSQL 16 focused invoices, migrations, and payment-observation suite: 74 passed, 0 failed, 0 ignored
• Full paykit-server-e2e: 240 passed, 0 failed; 3 pre-existing live-adapter tests ignored and not executed
• cargo test --locked -p paykit-server -- --test-threads=1: 486 passed, 0 failed, 0 ignored
• cargo fmt --all -- --check: passed
• cargo clippy --locked --workspace --all-targets -- -D warnings: passed
• cargo doc --locked --workspace --no-deps: passed
• exact identity, patch-digest, git diff --check, and git show --check gates: passed

Review caveats

• Approval applies only to exact commit and tree above. Any edit, rebase, conflict resolution, generated-file change, or version bump requires fresh independent review.
• README.md is a known merge hotspot against newer master. server.rs and persistence/invoices.rs overlap open PR feat: allowance intake in production #122; this PR does not absorb PR feat: allowance intake in production #122's USDT/allowance work.
• Ignored live-adapter tests require external Pubky/Electrum infrastructure and were not run.

Rollout boundaries

No production migration, deployment, release, tag, or external-adapter operation is performed by this PR. Migration 0024 is published unchanged and must be applied through human-controlled deployment. Locks payment-only integration remains blocked on human merge of this provider PR, immutable provider release, and human merge of Graph Stage 1 PR #120.

[ben-kaufman]

The expiry and payment-drain issues are fixed. Looks good.