Update project config for Go tool and port change

Add Go to .tool-versions, update .gitignore for Go build output and
cache, document seed data regeneration in README, and change API port
from 8000 to 8080 in docker-compose.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -31,6 +31,8 @@ docker compose exec api alembic -c /app/alembic.ini upgrade head
 
 ### Seed the Database
 
+The seeder reads from pre-generated JSON files in `backend/src/app/seeds/data/` (committed to the repo) and loads them into PostgreSQL. No external API access is needed — everything runs from local files inside the container.
+
 ```bash
 docker compose exec api python -m app.seeds
 ```
@@ -41,4 +43,34 @@ To seed and verify the data was loaded correctly:
 docker compose exec api python -m app.seeds --verify
 ```
 
-This loads game data, Pokemon, routes, and encounter tables for FireRed, LeafGreen, Emerald, HeartGold, and SoulSilver.
+This loads game data, Pokemon, routes, and encounter tables for FireRed, LeafGreen, Emerald, HeartGold, and SoulSilver.
+
+### Regenerating Seed Data
+
+The seed JSON files don't normally need regenerating. If you need to update them (e.g., to pull in new PokeAPI data), run the Go fetch tool against a local PokeAPI instance:
+
+1. Start a local PokeAPI (e.g., using [pokeapi/pokeapi](https://github.com/PokeAPI/pokeapi)):
+
+   ```bash
+   # In a separate directory
+   git clone https://github.com/PokeAPI/pokeapi.git && cd pokeapi
+   docker compose up
+   ```
+
+   This serves the API at `http://localhost:8000/api/v2` by default.
+
+2. Run the fetch tool (requires Go 1.22+):
+
+   ```bash
+   cd tools/fetch-pokeapi && go run .
+   ```
+
+   Set `POKEAPI_URL` if your instance is at a different address:
+
+   ```bash
+   POKEAPI_URL=http://localhost:9000/api/v2 go run .
+   ```
+
+   Use `--clear-cache` to discard cached API responses and re-fetch everything.
+
+3. Review and commit the updated JSON files in `backend/src/app/seeds/data/`.