[Draft] Wire initial Next.js app to Convex backend

[BASIC-BIT]

Problem

VRDex needs the initial web app and backend to connect through one real runtime path instead of existing as separate scaffolds.

Scope

• connect the initial Next.js app to the initial Convex backend
• add the minimum client/provider setup needed for app-to-backend communication
• expose one simple placeholder read path from the app into Convex
• confirm the app can render data coming from Convex
• keep the integration minimal and friendly to later auth, schema, and product work

Non-goals

• full product schema implementation
• auth integration
• billing integration
• production deployment setup
• full loading/error-state design system
• advanced data-fetching patterns beyond the first working path

Acceptance criteria

• the Next.js app can talk to Convex locally
• the app includes the minimum provider/client wiring required for that connection
• at least one placeholder query or read path is rendered in the app successfully
• the integration leaves room for later domain schema and feature work without forcing premature structure decisions

Likely docs to update

• README.md
• docs/planning/engineering-strategy.md
• docs/README.md
• any app/backend setup doc created during implementation

Soft dependencies

• #53 Scaffold initial Next.js web app
• #54 Bootstrap initial Convex backend

Soft dependents

• #9 Create base profile schema for people and communities
• #18 Implement multi-provider account login for v0.5 (Discord, Google, email/password)
• #19 Build public person profile page
• #21 Build public community profile page
• #31 Implement public search across people and communities