feat: add Tailcall config builder

[jamilahmadzai]

/claim #373

Summary

• Adds /app/config as a schema-driven Tailcall config builder that fetches the live runtime schema from tailcallhq/tailcall at page load.
• Renders config sections from the schema, including optional fields, repeatable arrays, object variants, numeric/boolean controls, and searchable enum inputs.
• Prunes and validates the generated config before export, then supports JSON, YAML, and GraphQL preview with copy/download actions.
• Adds JSON import for editing existing configs and a direct entry point from /playground.

Notes

• No new runtime dependencies or lockfile changes.
• Handles schema refs, allOf, oneOf, and anyOf so the UI follows schema changes without hardcoding field lists.
• Export actions stay disabled until there is at least one valid generated setting.

Validation

• npm ci
• npx prettier --write src/components/config-builder/ConfigBuilder.tsx src/pages/app/config.tsx src/components/playground/Playground.tsx
• git diff --check
• npm run build
• ./node_modules/.bin/cypress run --config baseUrl=http://127.0.0.1:3000 --spec cypress/e2e/config_builder_tmp.cy.ts against the generated production build, including desktop/mobile screenshots, JSON import, JSON export, GraphQL export, and playground link checks. The temporary spec was removed before commit.
• npm run typecheck -- --pretty false still fails on existing generated GraphQL/DocSearch typing issues outside this change; no errors are reported for the new config builder or touched playground files.

Payment method: Algora bounty-platform payout to GitHub user @jamilahmadzai.