fix(console): prevent pool volume count overflow

[GatewayJ]

Type of Change

• New Feature
• Bug Fix
• Documentation
• Performance Improvement
• Test/CI
• Refactor
• Other:

Related Issues

Fixes rustfs/backlog#1095

Summary of Changes

• widen PoolDetails.total_volumes to i64
• widen both pool dimensions before multiplication so the result cannot overflow
• reuse the same derivation in list and add-pool response paths
• document the widened OpenAPI contract and add overflow regression coverage

Checklist

• I have read and followed the CONTRIBUTING.md guidelines
• Passed make pre-commit (fmt-check + clippy + test + console-lint + console-fmt-check)
• Added/updated necessary tests
• Documentation: N/A; the generated OpenAPI contract is covered by a schema test
• CHANGELOG: N/A; this is a focused correctness fix
• CI/CD passed (pending GitHub Actions)

Impact

• Breaking change (CRD/API compatibility)
• Requires doc/config/deployment update
• Other impact: OpenAPI widens total_volumes from int32 to int64; the JSON field remains numeric

Verification

make pre-commit

Additional Notes

Every i32 * i32 result fits exactly in i64, so widening preserves the real volume count without clamping. Values above JavaScript's safe-integer range remain a theoretical client-side limitation; changing the field to a string would break the existing Console contract and is outside this fix.

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