feat: add egg groups to schema and query layer (2.15.19)

[seandonn-boston]

Summary

• Add eggGroup1 and eggGroup2 nullable string fields to the Pokemon Prisma model
• Expose as eggGroups: string[] in PokemonCardData interface via getPokemonById
• Filter nulls so the array contains 0, 1, or 2 entries depending on the species
• Update all test mocks (pokemon.test.ts, route.test.ts, search/route.test.ts) for type compliance
• 3 new test cases covering two groups, single group, and no groups (undiscovered)

Test plan

• Pipeline passes (10/10 steps)
• Typecheck clean — all PokemonCardData mocks updated with eggGroups
• 30 pokemon query tests pass (3 new egg group tests)
• No UI changes needed — egg groups are now available for future display components

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