[P2] Load project context globally on app entry

[kgarg2468]

Problem

Project list loading is concentrated in Data page, so non-Data entry points can have incomplete project context.

Scope

• Load project context centrally (app shell/top bar) so project picker and active context are available everywhere.

Acceptance Criteria

• Dashboard/Simulate/Report have populated project context without first visiting Data page.
• No duplicate/excessive fetch loops introduced.

Suggested Files

• components/layout/LayoutShell.tsx
• components/layout/TopBar.tsx
• lib/store/project-store.ts