fix(consumptions): keep selected month urls lowercase

[maxstue]

Summary

• Keep the consumptions month dropdown URL value on the canonical lowercase monthSchema values.
• Continue rendering localized month labels with formatMonth.
• Correct the month selector aria label from year to month.

Root Cause

The command item selection used the rendered month label as the selected value. For English labels this produced values like April, which failed the consumptions route search validation because the route expects lowercase enum values like april.

Validation

• pnpm --filter kijk-client build
• pnpm --filter kijk-client typecheck
• pnpm --filter kijk-client fmt
• pnpm --filter kijk-client lint
• pnpm dlx react-doctor@latest . --verbose --diff
• pnpm dlx fallow audit --format json --quiet --base main --explain

Refs KIJK-333

[linear-code]

KIJK-333