Simplify README and redesign OG image

[pushpak1300]

What does this PR do?

Rewrites the README in a simpler, Laravel-docs style and redesigns art/og.png using the Ship Fast Labs design system.

README

• Short intro, then Installation and a four-step Quick Start: define permissions, define roles, assign roles, check permissions.
• Optional extras (scoped roles, policies, super admins, grant:sync, caching, facade, config, commands, Filament, testing) follow as short sections.
• Removed the long table of contents and repeated explanations. All code examples are kept.

OG image (2560×1280)

• Built from the Ship Fast Labs design system tokens: pure black background, #B4FC6F lime, Pixelify Sans wordmark, Geist hook line, Silkscreen labels.
• Giant grant wordmark, the hook "permissions are just enums.", the large ship/fast/labs logo mark and a composer require line.

Type of change

• Bug fix
• New feature
• Refactor / code cleanup
• Documentation

Checklist

• Tests added or updated (docs and image only)
• composer lint passes (not run; no PHP changes)
• composer test passes (not run; no PHP changes)

🤖 Generated with Claude Code

https://claude.ai/code/session_019mo4fvMdmhHUffDkmpUDM2

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