feat(Flags): Add remove option to feature settings

[Dexter2099]

Feature settings currently show archive but not removal, which makes archive look like the only way to retire a feature. This adds the existing remove flow to the settings panel so users can delete a feature without returning to the feature list row menu.

Changes

• Adds a Remove Feature action to the feature settings panel.
• Reuses the existing typed confirmation and remove-feature toast flow.
• Keeps removal behind the existing delete-feature permission and permanent-tag protection.
• Covers the remove-button disabled states with a focused unit test.

Closes #7896

Validation

• npm run test:unit -- --testPathPatterns=FeatureSettingsTab.utils.test.ts
• npx eslint --fix web/components/modals/create-feature/index.tsx web/components/modals/create-feature/tabs/FeatureSettingsTab.tsx web/components/modals/create-feature/tabs/FeatureSettingsTab.utils.ts web/components/modals/create-feature/tabs/__tests__/FeatureSettingsTab.utils.test.ts
• npx tsc --noEmit --pretty false 2>&1 | Select-String -Pattern 'web/components/modals/create-feature/index.tsx|web/components/modals/create-feature/tabs/FeatureSettingsTab.tsx|web/components/modals/create-feature/tabs/FeatureSettingsTab.utils.ts|FeatureSettingsTab.utils.test.ts' returned no touched-file errors.
• npm run typecheck is not clean on this checkout due existing unrelated errors, beginning with common/constants.ts(435,36) and common/hooks/useCollapsibleHeight.ts(36,15).

Review effort: 2/5

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