Create `@h3ravel/contracts` package for shared framework interfaces

[3m1n3nc3]

Description

Introduce a new @h3ravel/contracts package to house all shared interfaces, types, and contracts used across the H3ravel ecosystem.

This package will serve as the single source of truth for cross-package abstractions and must remain implementation-agnostic.

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Goals

• Decouple implementations from interfaces
• Improve type consistency across packages
• Avoid circular dependencies between core packages

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Scope

The package may include (but is not limited to):

• Application contracts
• Service provider contracts
• HTTP-related contracts (Request, Response, Middleware)
• Queue, Event, Cache, Logger contracts
• Filesystem and Storage contracts

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Tasks

• Create new package @h3ravel/contracts
• Move existing shared interfaces into this package
• Define missing core contracts where needed
• Update dependent packages to import from @h3ravel/contracts
• Add basic documentation explaining usage and conventions
• Add type-only exports where applicable

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Acceptance Criteria

• No concrete implementations in this package
• All exports are interfaces, types, or abstract classes
• Other packages depend on contracts, not implementations
• No runtime side effects

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Difficulty

Intermediate