Add guarded limit reset action and bump 0.5.1

[woffko]

Summary

Add a guarded RESET action to the Usage LIMITS card and bump CoMon to 0.5.1.

What changed

• Add a standalone Norton Commander-style RESET button inside the right-center of the Usage LIMITS card.
• Enable the button only when:
  • the account has at least one available reset credit;
  • at least one displayed limit has reached 0% remaining.
• Show a confirmation dialog before consuming a reset credit.
• Call account/rateLimitResetCredit/consume with a unique idempotency key.
• Process reset requests serially in the existing limits worker.
• Refresh rate limits and account usage immediately after the reset response.
• Persist a one-hour cooldown before sending the irreversible request.
• Show disabled, in-flight, and cooldown states directly on the button.
• Preserve the cooldown after ambiguous errors to prevent accidental double consumption.
• Handle all reset outcomes: reset, nothingToReset, noCredit, and alreadyRedeemed.

Safety

The reset RPC is not sent unless the cooldown has first been written successfully to state.json.

A separate bounded channel prevents routine refresh requests from displacing the user action. The backend remains authoritative, and the UI guard uses a small floating-point
tolerance around 0% remaining.

UI

The RESET button is independent of the card border, vertically centered, and aligned to the card's right inner edge.

Its active state uses the same inverse-video treatment as the YES/NO dialog buttons. Disabled, in-flight, and cooldown states remain visually distinct.

Validation

• 167 tests passed.
• cargo fmt --check
• bash scripts/check-ascii.sh
• Visual verification at 180×45.
• Release binary built and installed locally as comon 0.5.1.

The existing upstream theme and heatmap Clippy warnings are unchanged by this PR.