Add drizzle-kit update command

[galenzo17]

Summary

Implements #388 - adds a new CLI command to update drizzle-orm and drizzle-kit to their latest versions.

• Automatically detects package manager (npm, pnpm, yarn, bun)
• Preserves version prefixes (^, ~)
• Supports --beta, --kit-beta, --orm-beta flags for prerelease versions
• --dry-run to preview changes without modifying files
• --skip-install to update package.json without running install

Usage

# Update to latest stable versions
drizzle-kit update

# Preview what would be updated
drizzle-kit update --dry-run

# Update to beta versions
drizzle-kit update --beta

# Update only drizzle-kit to beta
drizzle-kit update --kit-beta

# Skip running package manager install
drizzle-kit update --skip-install

Test plan

• Unit tests for CLI flag parsing
• Unit tests for getLatestVersion (tag priority)
• Unit tests for updatePackageInJson (edge cases: workspace:*, git URLs, etc.)
• Unit tests for detectPackageManager
• Unit tests for getInstallCommand
• All 36 tests passing

Closes #388