fix(db): exclude legacy Pinata fallback rows from IPFS state queries

record_pinned_cid now uses a WHERE clause to only replace cid when it is
NULL (new Pinata-only) or equals pinata_cid (legacy Pinata-only fallback).
has_ipfs_cid and filter_ipfs_pinned_oids add AND cid IS DISTINCT FROM
pinata_cid so legacy rows with cid = pinata_cid are not treated as
IPFS-pinned.

Author: Gravirei

crates/gitlawb-node/src/db/mod.rs

@@ -2267,7 +2267,7 @@ impl Db {
             .collect())
     }
 
-    /// Returns true if this object has a real local IPFS CID (not a legacy
+    /// Returns true when this object has a real local IPFS CID (not a legacy
     /// Pinata fallback where cid was set to pinata_cid for new rows).
     pub async fn has_ipfs_cid(&self, sha256_hex: &str) -> Result<bool> {
         let row = sqlx::query(