Refactor extensions to heapless architecture

[JanPetterMG]

Refactors the extensions subsystem to remove dynamic memory usage and transition to a heapless architecture.

Changes

• Eliminated heap allocations across extensions
• Reworked extension storage and lifecycle management to use static/compile-time constructs
• Simplified ownership model by removing dynamic containers (std::vector, new, etc.)
• Updated extension interfaces where required to support heapless usage
• Improved consistency across extension implementations

Motivation

• Reduce heap fragmentation and runtime instability on constrained ESP32 targets
• Improve determinism and predictability
• Align with broader project direction of minimizing dynamic allocation

Impact

• Lower memory overhead and improved runtime stability
• Slight increase in compile-time complexity
• Potential breaking changes for extension implementations relying on heap usage

Notes

• This change is internal and primarily affects extension handling
• No user-facing configuration changes expected
• Forms a foundation for further compile-time optimizations