docs(readme): replace stale screenshot with project overview

[iamjr15]

Summary

• remove the unrelated ClearTax screenshot and its 432 KiB repository asset
• add truthful CI, runtime, TypeScript, and license badges
• add concise product navigation and a capability overview for first-time readers
• correct nearby connected-app wording and prerequisite punctuation

Decisions

• Removed the screenshot instead of replacing it with a private-account or fabricated product image.
• Kept badges limited to verifiable repository facts: the real CI workflow, pinned Node and pnpm versions, strict TypeScript, and the exact PolyForm license.
• Preserved the existing architecture, self-hosting, development, security, and license guidance.

Architecture and migrations

• No runtime architecture, dependency, deployment, schema, or migration changes.

Verification

• pnpm lint
• pnpm typecheck
• pnpm turbo build --force with the non-secret static-check build environment
• pnpm deadcode
• pnpm architecture:check
• pnpm turbo skills:build
• git diff --check
• validated every README local path and external URL
• rendered the README through GitHub's GFM API and confirmed badges, table, links, and Mermaid markup