Fix pokemon moves lookup assuming contiguous ids

[santichausis]

Problem

PokemonDetailSerializer.get_pokemon_moves looks up VersionGroup and MoveLearnMethod summaries by list position (id - 1), assuming both tables form a contiguous 1-indexed sequence with no gaps.

Any gap in either table (e.g. a deleted row, or a new entry inserted with an id that doesn't match its position) causes the wrong version group / move learn method to be returned for a move, or raises an IndexError.

Fix

Build a dict keyed by the actual id instead of relying on list position, so lookups are correct regardless of gaps in the id sequence.

Test plan

• Added test_pokemon_moves_with_non_contiguous_version_group_and_method_ids, which creates and deletes a VersionGroup and a MoveLearnMethod to force a gap, then asserts the pokemon endpoint still returns the correct version group / move learn method.
• Verified this test reproduces the IndexError against the old code and passes with the fix.
• manage.py test pokemon_v2 passes (55 tests).
• black --check passes.

Fixes #1567

[Naramsim]

Hi! Thanks for the submission! The passing tests tell me that everything is working as expected. I honestly don't understand very well the additional python test you added, but that's my lack of knowledge. I'll merge this, thanks for the contribution!

Can you spot in the code base other issues like this one?

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[santichausis]

Thanks for merging! Yes, I found at least one more spot with the same pattern: LocationAreaDetailSerializer.get_encounters in pokemon_v2/serializers.py (around line 1222) does the same version_data[ver["version"] - 1] list-index lookup instead of keying by the actual Version id. It has the same failure mode as this one (wrong version returned, or IndexError, if the version ids aren't a contiguous 1-indexed sequence).

This one was actually touched before in #1314 (closed without merging), so there's some history there. Happy to open a follow-up PR fixing it the same way (dict keyed by id) with a regression test, if that's useful — let me know.