feat(logs): populate send log detail and fix dedup re-claim condition

- dispatch: attach per-send detail (title/url/description/match/provider)
  so the admin log view shows message context, not just a bare ok flag
- idempotency: compare dedup expiry against claimed_at instead of the new
  expires_at so non-expired duplicates are rejected and expired keys re-claim

tests/d1-stores.test.ts

@@ -50,7 +50,7 @@ function createMockD1(): {
         dedupKeys.set(key, { claimedAt, expiresAt });
         return { success: true, meta: { changes: 1 } };
       }
-      if (existing.expiresAt < expiresAt) {
+      if (existing.expiresAt < claimedAt) {
         dedupKeys.set(key, { claimedAt, expiresAt });
         return { success: true, meta: { changes: 1 } };
       }