refactor(conversation): remove budget display

[saurya]

HUMAN:

• A human has tested these changes.

AGENT:

This pull request was created by an AI agent (OpenHands) on behalf of the user.

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Why

The conversation metrics dialog still displayed per-task budget information, including “No budget limit,” after that UI was removed from Agent Canvas.

Summary

• Remove the conversation metrics budget display and its helper components.
• Stop passing per-task budget data through the metrics dialog cost section.
• Remove the dedicated, now-unused budget usage translation while preserving organization and payment budget controls.

Issue Number

N/A

How to Test

1. Run cd frontend && npm install.
2. Run npm run check-translation-completeness.
3. Run npm run lint.
4. Run npm run build.
5. Create or open a conversation, open the metrics dialog, and verify total cost remains visible without a budget bar, budget usage text, or “No budget limit.”

Validation performed:

• Translation completeness passed.
• Lint and typecheck passed with five pre-existing warnings.
• Production build passed.
• Frontend and backend pre-commit hooks passed.
• Full frontend suite: 303 test files passed; three unrelated use-websocket.test.ts cases failed locally due to MSW connection handling, plus an unrelated missing ProgressEvent environment error.

Video/Screenshots

Pending human verification.

Type

• Bug fix
• Feature
• Refactor
• Breaking change
• Docs / chore

Notes

Organization and payment budget controls still use CONVERSATION$NO_BUDGET_LIMIT and are intentionally unchanged.

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Enterprise server image for this PR:

ghcr.io/openhands/enterprise-server:sha-b0e966a

[github-actions]

Coverage report

This PR does not seem to contain any modification to coverable code.