Add Integration Readiness coming-soon card

[raphael-solace]

Summary

• Adds a new "Integration Readiness" card to the Coming Soon section of the landing page, alongside the existing Middleware Explorer card.
• The tool combines a maturity assessment with an ROI perspective: a quick self-serve diagnostic that scores integration maturity across axes like real-time capability, decoupling, event governance, AI-readiness, and multi-cloud reach — then outputs personalised benchmarks and tailored recommendations mapped to Solace capabilities.
• Serves as both a lead magnet and a tool that arms champions with budget justification for vendor consolidation.

Changes

• index.html: Added one new card--coming-soon div following the exact same pattern (classes, structure, animation delay, aria attributes) as the Middleware Explorer card.

Test plan

• Verify the card renders correctly on desktop and mobile viewports
• Confirm the card is non-interactive (opacity, cursor, no hover effects) matching the Middleware Explorer card
• Check that no existing content or styles were changed