fix: add reset action for network proxy edits

[neptune-me]

Pull Request

Related Issue

Closes #1728

Description

Adds a Reset action for unsaved Network Proxy edits.

• Tracks the last successfully loaded or saved proxy URL separately from the editable value.
• Enables Save only when the normalized proxy value has changed.
• Enables Reset whenever the displayed value differs from the saved baseline, including whitespace-only edits.
• Restores the saved value without writing or removing environment variables.
• Updates the reset baseline only after a successful save.
• Preserves URL validation, error handling, and the existing Restart to Apply behavior.
• Uses the existing Button and Input primitives, semantic design tokens, and setting.reset translation.
• Adds focused tests under the current unit-test structure.

Testing Evidence (REQUIRED)

Automated validation:

• npm test -- test/unit/components/GeneralSettingsProxy.test.tsx — 1 test file passed, 9 tests passed.
• npm run type-check — passed.
• npx eslint src/components/Settings/General/index.tsx test/unit/components/GeneralSettingsProxy.test.tsx --no-warn-ignored — passed.
• npm run check:design-token-usage — passed.
• git diff --check — passed.
• Repository pre-commit hooks — passed.

Focused tests cover loading a saved or empty proxy, editing and resetting without persistence writes, successful and failed save baselines, invalid URLs, whitespace-only edits, saving an empty proxy, and disabling Reset while a save is in flight.

Manual macOS verification:

• Confirm the saved proxy loads with Save and Reset disabled.

• Edit the proxy and confirm Save and Reset become enabled.

• Click Reset and confirm the saved value is restored.

• Save a valid edit and confirm Restart to Apply appears.

• Attach a screenshot or screen recording below.
  https://drive.google.com/file/d/1vLOe4r7cfVhKAjO5--k3NpZ8L8SlfcNJ/view?usp=sharing

• I have included human-verified testing evidence in this PR.

• This PR includes frontend/UI changes, and I attached screenshot(s) or screen recording(s).

• No frontend/UI changes in this PR.

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Contribution Guidelines Acknowledgement

• I have read and agree to the Eigent Contribution Guideline

[Douglasymlai]

@neptune-me Thanks for your contribution. LGTM