Feature/leaderboard pagination

[Truphile]

I have implemented the agent clustering logic and fully integrated it into
the system's SSE stream and frontend map according to your criteria.
Here is what was done:

1. Clustering Algorithm: Created position-cluster.ts which provides the
   clusterPositions method using the Haversine formula to cluster agents
   within the given gridSizeKm (default: 5km).
2. SSE Stream Updates: Created a new route.ts SSE endpoint which
   tracks the query parameter ?cluster=true&gridSize=5 . When clustering is
   toggled on, it emits a agent.positions.clustered.snapshot event initially
   and agent.positions.clustered full state events whenever any internal
   position change is detected by subscribeAgentPositionDeltas . When
   cluster=false , it behaves equivalently to the legacy individual delta
   stream.
3. Map Component UI: Refactored the Map structure to support reading query
   parameters.
   • Added ?cluster=true query check using useSearchParams() inside
   AgentsMap.tsx.
   • In LeafletMap.tsx, when clustering is active, it conditionally
   renders custom blue circle markers featuring a numeric badge using L.
   divIcon displaying the exact cluster count .
4. Unit Tests: Wrote tests covering the clustering logic at position-
   cluster.test.ts
   satisfying the "3 agents within 2km -> 1 cluster of 3" criteria.

closes #267

[sonarqubecloud]

Quality Gate passed

Issues
16 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud