fix: remove f-prefix from empty strings (ruff F541)

Author: Lars Kroehl

src/moltrust_mcp_server/server.py

@@ -2356,7 +2356,7 @@ async def mt_get_track_provenance(
         f"Credential ID: {data.get('id')}",
         f"Agent DID: {subj.get('agentDid')}",
         f"Human Name: {subj.get('humanName', 'N/A')}",
-        f"",
+        "",
         f"Track: {track.get('title')}",
         f"Description: {track.get('description', 'N/A')}",
         f"Tool: {track.get('tool')}",
@@ -2365,11 +2365,11 @@ async def mt_get_track_provenance(
         f"Rights: {track.get('rights')}",
         f"ISRC: {track.get('isrc', 'N/A')}",
         f"Session: {track.get('session', 'N/A')}",
-        f"",
+        "",
         f"Track Hash: {prov.get('trackHash')}",
         f"EU AI Act: {prov.get('euAiActCompliance')}",
         f"Issued: {prov.get('issuanceDate')}",
-        f"",
+        "",
         f"Chain: {anchor.get('chain')}",
         f"Anchor TX: {anchor.get('anchorTx', 'pending')}",
         f"Anchor Block: {anchor.get('anchorBlock', 'pending')}",