token: add spending-condition inspection helpers and token_secrets() (#1124)

* token: add Token::token_secrets() and spending-condition helpers

- New helpers on Token that do not require mint keysets:
  - spending_conditions()
  - p2pk_pubkeys()
  - p2pk_refund_pubkeys()
  - htlc_hashes()
  - locktimes()
- Introduce token_secrets() to unify V3/V4 proof traversal and avoid duplication
- Bypass short->long keyset-id mapping since only Secret is needed for conditions
- Use &Secret for TryFrom to fix compile error

crates/cdk-postgres/src/lib.rs

@@ -335,10 +335,9 @@ mod test {
 
         let db_url = format!("{db_url} schema={test_id}");
 
-        let db = MintPgDatabase::new(db_url.as_str())
+        MintPgDatabase::new(db_url.as_str())
             .await
-            .expect("database");
-        db
+            .expect("database")
     }
 
     mint_db_test!(provide_db);