[copacabanaservice01]

Summary

• limit the Add Scalar Field selector to the numeric types supported by Zvec add_column
• default new scalar fields to INT32
• reject unsupported post-creation field types at the API validation boundary
• preserve duplicate-field coverage with a supported numeric field

Testing

• pnpm --filter frontend lint
• pnpm --filter frontend typecheck
• pnpm --filter frontend test (329 passed)
• pnpm --filter frontend build
• uv run ruff check zvec_studio/schemas/collection.py tests/unit/test_collections_schemas.py tests/integration/test_collections_router.py
• uv run mypy zvec_studio
• uv run pytest -q (575 passed, 4 skipped on Windows)

Closes #10