chore: establish M0 baseline quality and expose Google sign-in

[TechAaroorian]

Summary

Completes the SlotSyncro M0 baseline-quality milestone and exposes Google authentication alongside GitHub login.

Changes

• Fixed existing application and marketing lint issues
• Added missing ESLint configuration and dependencies
• Improved the mobile viewport hook using useSyncExternalStore
• Excluded generated coverage output from linting
• Declared the Prisma client dependency explicitly
• Updated the workspace to pnpm 11.24.0
• Reconciled the pnpm lockfile and workspace build configuration
• Added safe environment-variable templates
• Passed required OS environment variables through Turbo strict mode
• Added Google sign-in to the authentication UI
• Updated email-invitation feature statuses from Partial to Current
• Added the M0 baseline audit documentation

Verification

• Lint: 2/2 tasks passed
• Tests: 11 files and 45/45 tests passed
• Prisma Client generation: passed with Prisma 7.9.1
• Production build: 3/3 tasks passed
• Google OAuth callback: confirmed working
• Git worktree: clean

Notes

• Google and GitHub accounts with the same email are not automatically linked. Secure provider linking should be implemented separately.
• Next.js reports a non-blocking deprecation warning for middleware.ts; migration to proxy.ts can be handled in a follow-up.
• No secrets or secret-bearing .env files are included.

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	99.06%	106 / 107
🔵	Statements	98.16%	107 / 109
🔵	Functions	100%	13 / 13
🔵	Branches	82.14%	46 / 56

File Coverage

No changed files found.

Generated in workflow #24 for commit 7227fc0 by the Vitest Coverage Report Action