Remove old root-level Express routes

[kmcginnes]

Parent PRD

• Parent Simplify client-server relationship by removing proxy URL from connection config #1618

What to build

Remove the old non-prefixed Express routes (/gremlin, /sparql, /openCypher, /summary, /pg/statistics/summary, /rdf/statistics/summary, /logger, /status, /defaultConnection) that were kept for backward compatibility during the transition. After this, the only API path is /api/*. Clean up any remaining references to the old URL patterns.

This is the final cleanup slice that completes the migration.

Type: HITL — requires review before completion.

Acceptance criteria

• Old root-level routes are removed from the Express server
• Only /api/* routes remain for API endpoints
• No client code references old root-level API paths
• Tests verify old routes return 404
• All existing tests pass with the new route structure

Blocked by

• Blocked by Create apiBase module and wire client fetch to /api/* #1621
• Blocked by Decouple ServerLoggerConnector from connection #1623
• Blocked by Simplify defaultConnection fetch and backward-compat env vars #1626

User stories addressed

• User story 9
• User story 13