Add Applied Filters Tracking to Filterable Engine

[kettasoft]

This pull request introduces a complete mechanism for recording all filters that were actually applied during the filtering lifecycle.
The feature ensures that only filters that passed validation, logic checks, and execution are stored, allowing consumers of the engine to reliably inspect the final filtering state.

Key Features Added:

• Applied Filters Registry
A dedicated internal structure for collecting and exposing the filters that were successfully applied, including their field, operator, value, and any relevant context.

• Integration With Engine Execution Flow
Filters are added to the registry only after passing through payload parsing, value sanitization, clause building, and successful execution via the commit pipeline.

• Public Accessor
A clean API for retrieving the applied filters from outside the engine.
This enables features such as debugging, analytics, UI filter visualization, or caching keys based on final applied filters.

• Non-intrusive Design
The tracking system does not change the behavior of any existing engines or filters.
It works automatically under the hood and integrates seamlessly with strict/permissive modes as well as skipping logic.

• Unit Tests Included
Tests verify:
– applied filters are recorded correctly
– skipped or invalid filters are not added
– structure of stored filters remains consistent
– behavior works across typical engine execution scenarios

Why This Matters:
Tracking applied filters opens the door to more powerful features like user-facing filter summaries, debugging tools, API responses with filter metadata, and smarter caching strategies.