chore: remove unused @solana/web3.js and ethers dependencies

[QuenumGerald]

Motivation

• Reduce install footprint and avoid pulling large, unused SDKs and mail libs by removing @solana/web3.js, ethers, nodemailer and its types from the project dependency metadata.

Description

• Deleted @solana/web3.js, ethers, nodemailer and @types/nodemailer from package.json dependencies/devDependencies.
• Removed the corresponding node_modules entries and metadata for those packages from package-lock.json to keep the lockfile consistent.
• Added a short README.md installation note about blockchain SDKs and native better-sqlite3 builds to explain potentially longer installs.

Testing

• No automated tests were run because this change only updates dependency metadata (no code behavior changed).

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Codex Task