fix: add Arcanine to Champions dex

[hamuhei1412]

Change description

Adds Arcanine to the Champions Pokédex.

The Champions Pokédex uses pokedex_id = 36, and Arcanine's species ID / National Pokédex number is 59.

This adds the following entry to data/v2/csv/pokemon_dex_numbers.csv:

59,36,59

AI coding assistance disclosure

I used Codex and ChatGPT to help inspect the existing CSV structure, make the one-line data change, and draft the PR wording. I manually reviewed the proposed change and verified that pokemon_dex_numbers.csv is species-based.

Contributor check list

• I have written a description of the contribution and explained its motivation.
• I have written tests for my code changes (if applicable).
• I have read and understood the AI Assisted Contribution guidelines.
• I will own this change in production, and I am prepared to fix any bugs caused by my code change.