feat: clean up README and .env.example (P0-09)

[EKF0]

This PR cleans up and production-hardens the documentation and environment configurations of the platform (P0-09).

Changes:

• README.md: Replaced generic Google AI Studio applet boilerplate with a detailed developer overview of BagFi's Solana hybrid architecture, layout, features, and setup instructions.
• .env.example: Stripped outdated Google variables and deprecated EVM parameters, structuring variables logically into Supabase, Solana RPC, and Bags.fm blocks.
• Added full automated verification with Next.js build compilation and Vitest suites successfully passing.

[vercel]

Deployment failed with the following error:

Hobby accounts are limited to daily cron jobs. This cron expression (*/5 * * * *) would run more than once per day. Upgrade to the Pro plan to unlock all Cron Jobs features on Vercel.

Learn More: https://vercel.link/3Fpeeb1

[supabase]

This pull request has been ignored for the connected project zgqlbqmebjnsaxraqwmt because there are no changes detected in supabase directory. You can change this behaviour in Project Integrations Settings ↗︎.

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