[Issue #8597] Add Create Opportunity button to opportunities list

[desaiamit]

Summary

Work for #8597

Changes proposed

• Added a Create Opportunity button to the Opportunities list page for the populated opportunities state.
• Positioned the button on the right side of the opportunities summary row, matching the design direction.
• Added translation key Opportunities.createOpportunityButton with value Create Opportunity.
• Added test coverage for button visibility and destination URL.

Context for reviewers

• Button appears when opportunities are present (table state), consistent with requested placement.

Validation steps

• Run lint:
  • cd frontend && npm run lint
• Run type-check:
  • cd frontend && npm run ts:check
• Run targeted tests:
  • cd frontend && npm run test -- opportunities/page.test.tsx --watch=false
• Manual check:
  • Open Opportunities page
  • Confirm Create Opportunity button is right-aligned on the opportunities summary row
  • Confirm button navigates to the Create Opportunity page