Prepare cup/map data package for first closed alpha

Description

The first closed alpha needs at least one complete, playtested cup with maps that have correct ring placements, boost configs, and difficulty tuning. Currently no official map data package exists in the repository.

Acceptance Criteria

• At least 1 cup with 3 maps is created using the setup plugin
• Each map has a minimum of 8 rings with correct sequential ordering
• Each map has a configured spawn point, finish trigger, and boost count
• Ring positions are exported as JSON via the setup plugin and committed to server/src/main/resources/maps/
• Internal playtest by at least 2 players validates that all rings are reachable and the cup can be completed without bugs
• The data package is loadable by CupService / MapService without errors on server start

Technical Details

• Use the setup plugin (plugins/setup) to place rings and export config
• JSON format defined by GsonFileHandler in shared/common
• Maps should use the Anvil world format (already supported)

Dependencies

• Setup plugin is already functional (no code changes needed)

Estimate

M

Start with the setup plugin at plugins/setup and the JSON format handled by GsonFileHandler in shared/common. Create and export one three-map cup, committing the JSON files to server/src/main/resources/maps/. Verify CupService and MapService load the package on server start, then have two players confirm every ring is reachable and the cup completes without bugs.