feat: Add PSR-16 caching support to JsonLoader

Adds PSR-16 caching to JsonLoader for inventory JSON files. By default,
uses an in-memory ArrayAdapter that deduplicates HTTP requests within
a process. For persistent caching across CLI invocations, inject any
PSR-16 compatible cache implementation.

Features:
- PSR-16 interface: Use any compatible cache implementation
- In-memory default: Automatic request deduplication
- Multi-tier support: Use Symfony ChainAdapter for memory + filesystem
- Configurable TTL: Default 1 hour, customizable per use case
- Hash-based keys: Uses xxh128 for URL to cache key mapping

Performance impact: ~53% faster rendering for interlink-heavy
documentation by avoiding repeated HTTP requests.

Author: CybotTM