feat(api): map persistence layer with seed/edit precedence (#3)

[Aduersarius]

Closes #3.

Summary

• Adds the Etapa 0 map persistence layer using a measured multi-table schema: game_maps (metadata + npcs/specials), relational game_map_palette, and compact game_map_grids.rows JSONB (not 2.9M tile rows).
• Idempotent importer via import-game-maps / import-game-data maps.
• Seed vs edited precedence: import seeds with is_edited=false and keeps serving files until an admin edit; edited maps are served from DB and revisioned in game_data_revisions (kind=maps) with checksums.
• Admin + internal game-data map endpoints; unit + integration tests.

Differentiation vs open PRs

• vs feat(api): add editable map persistence layer #37: single JSONB game_maps document and DB-as-soon-as-row-exists. This PR follows the issue table split (metadata/palette/grid), documents the tile-row measurement decision, and only serves DB when is_edited=true so imported seeds still fall back to files.
• vs feat(api): map persistence layer, fallback reader and revision tracking (#3) #71: broad kitchen-sink (extra services, frontend, protocol package, unrelated tests). This PR stays scoped to the persistence layer and existing repositories/import/game-data patterns.

Verification

• Schema + repository + route wiring in place.
• Tests: api/src/tests/mapData.unit.test.ts, api/src/tests/game-maps.integration.test.ts (integration no-ops without DB).
• Local install/tsc blocked in agent session; CI should cover compile/test.

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