- Add missing #include <algorithm> for std::count in data_handlers.cpp
- Fix handle_list_data() to check entity existence before source_ids
- Fix handle_put_data_item() to mirror GET logic for full_topic_path
- Change discovery_handlers.hpp to use #pragma once
- Add Cap::FAULTS to handle_get_app() capabilities list
- Add entity_id to source_ids in get_area_data/get_function_data
- Fix direction='both' detection in collect_topics_from_app/component

These changes ensure:
- Consistent include guard style across codebase
- Correct 200/404 for empty vs missing entities
- No double slash in topic paths for PUT
- Accurate pub/sub direction metadata in aggregated responses

…andlers

Add integration tests for aggregated data endpoints:
- test_109: GET /areas/{area_id}/data for valid area
- test_110: GET /areas/{area_id}/data for nonexistent area
- test_111: GET /areas/root/data for system-wide aggregation
- test_112: GET /areas/{area_id}/data returns 200 for empty areas
- test_113: GET /functions/{function_id}/data for valid function
- test_114: GET /functions/{function_id}/data for nonexistent function
- test_115: GET /functions/{function_id}/data rejects invalid IDs

Fix existing tests for unified handler error messages:
- Update tests to expect 'Entity not found' / 'Invalid entity ID'
- Update tests to use 'entity_id' parameter in error responses
- Add readiness helpers to tests 07-10 for discovery race condition
- Allow direction='both' in topic data assertions
- Use 'aggregated_from' field name in new tests

Apply clang-format to handler files.

Changes:
- Fix get_area_data() to recursively traverse subareas using area_to_subareas_
  for proper area hierarchy aggregation behavior
- Fix handle_list_data() to use topic.name as ID instead of normalized form,
  making IDs directly usable for GET/PUT calls (clients URL-encode as needed)
- Fix _ensure_app_data_ready() helper to poll /apps/{id}/data endpoint
  instead of /apps/{id} to match what tests actually depend on
- Fix unused topic_names variable in test_111 by adding it to print output
- Fix function discovery: call discover_functions() in refresh_cache() and
  pass results to thread_safe_cache_.update_all() (was passing empty {})
- Apply clang-format to modified files

This fixes issues with:
- Area data not aggregating topics from subareas
- Data list IDs not being usable for subsequent GET/PUT item requests
- Test flakiness due to polling wrong endpoint
- Function data/operations endpoints returning 404 (functions not in cache)

- Add topic_type_cache_ member for O(1) topic type lookup
- Add update_topic_types() writer method and get_topic_type() reader method
- Populate topic types during gateway refresh_cache()
- Use cached types in handle_list_data() instead of discover_all_topics()

This avoids expensive ROS graph queries on every /data request,
which could add up on systems with hundreds of topics.

Addresses review comment from mfaferek93.

Add DataAggregationTest fixture to test_entity_resource_model.cpp with
tests covering:
- AppDataReturnsOwnTopicsOnly: verify app returns only its own topics
- ComponentDataAggregatesFromHostedApps: verify component aggregates
  topics from itself and hosted apps
- DirectionMergesToBothWhenPubAndSub: verify direction merging when
  same topic is published and subscribed
- AreaDataAggregatesFromAllComponents: verify area aggregates from
  all components in hierarchy
- GetEntityDataAutoDetectsType: verify auto-detection of entity type
- UnknownEntityReturnsEmptyData: verify empty result for nonexistent entity