feat(project): Add .cursorrules with Next.js 15+, Supabase, and ProjectDocs context management

[kryptobaseddev]

Adds a .cursorrules file that defines development standards for Next.js 15+ with App Router and Supabase integration, alongside a ProjectDocs-based context management system. Key features:

• Establishes ProjectDocs/contexts/ for maintaining project context files
• Implements Build_Notes system for tracking development tasks with clear phase progression
• Defines Next.js 15+ best practices with React Server Components and App Router
• Structures Supabase integration with domain-driven schema organization
• Sets up Shadcn UI component and styling standards
• Enforces mobile-first PWA development approach
• Implements systematic task breakdown and progress tracking through build notes

The rules are optimized for projects using Next.js 15+, Supabase, Shadcn UI, and require a ProjectDocs folder in the root directory to maintain project context and reduce AI hallucinations during development. Each build note corresponds to a specific task group and phase, helping maintain focused development contexts when working with Cursor AI Agent.