feat(tips): stage 4 — claim / clawback / confirm-sweep + sweep reconciler (money-out)

Escrow settlement, audited guards ported verbatim:
- mark_tip_claiming: status IN('pending','claiming') AND confs>=required AND
  funding_amount_verified AND sweep_confirmed_at IS NULL (double-claim guard).
- confirm_tip_sweep: RECORD-not-settle, first-recorder-wins (COALESCE +
  sweep_txid IS NULL OR =$3) — RBF-steal safe; reconciler owns claiming->claimed.
- confirm_sweep_onchain: SOLE writer of 'claimed', one-way status='claiming' AND
  sweep_confirmed_at IS NULL lock; settles only after on-chain sweep confirms to
  per-asset depth (btc/ltc 1, wow 4, xmr 10).
- clawback: 5-status set incl 'cancelled', blocked once sweep_confirmed_at set.
- revert_sweep_on_reorg: only from 'claimed', re-opens to 'claiming' + clears txid.
- sweep_reconciler: address-history-driven (not recorded txid), pick_winner
  (earliest height, lexi-smallest tie), pg advisory locks on a pinned conn for
  single-instance safety; reorg pass reverts only on affirmative vanish, never on
  probe error. DMs stubbed, exactly-once stamps kept.
- POST claim/confirm-sweep/clawback endpoints + openapi.
- 16 integration + 12 reconciler unit tests; build clean; SocialTipRow dead_code
  allow removed (all fields now read).

src/api/openapi.rs

@@ -73,6 +73,9 @@ use utoipa::OpenApi;
         crate::api::tips::get_public_social_tip,
         crate::api::tips::cancel_social_tip,
         crate::api::tips::attach_funding,
+        crate::api::tips::claim_social_tip,
+        crate::api::tips::confirm_sweep,
+        crate::api::tips::clawback_social_tip,
     ),
     components(schemas(
         crate::api::health::HealthResponse,
@@ -170,6 +173,10 @@ use utoipa::OpenApi;
         crate::api::tips::PublicTipInfo,
         crate::api::tips::CancelTipResponse,
         crate::api::tips::AttachFundingRequest,
+        crate::api::tips::ClaimTipResponse,
+        crate::api::tips::ConfirmSweepRequest,
+        crate::api::tips::ConfirmSweepResponse,
+        crate::api::tips::ClawbackTipResponse,
     )),
     tags(
         (name = "system", description = "Service health and metadata."),