[Electric 2.0] Update Homepage for 2.0 Launch

[KyleAMathews]

Goal

Reflect Electric 2.0 positioning on main site

Scope

• Hero messaging: "Query-driven sync with your stack"
• Feature callouts: subqueries, TanStack DB
• Update /website/index.md and home components

Dependencies

All features shipped, messaging finalized

Acceptance Criteria

Homepage tells complete 2.0 story

Context

Part of Electric 2.0 launch. The homepage is the first thing visitors see - it needs to communicate the complete 2.0 vision.

[smazurov]

Is there a timeline for 2.0 launch and a list of breaking changes?