[WOOMOB-2073] Add analytics tracking for POS FTS search. Removes FF

[kidinov]

Description

Fixes WOOMOB-2073

Adds analytics tracking for POS Full-Text Search to measure search performance, ranking quality, and indexing overhead. This PR also includes the full FTS stack from parent branches (search implementation with relevance ranking, UI wiring with variation support) and removes the POS_PRODUCTS_FTS feature flag to make FTS always-on.

Analytics events added (as agreed in the P2 post):

• search_results_fetched — tracks local FTS search latency, result count, and search method
• fts_index_built — tracks FTS index build duration and size during sync (Android only)
• pos_search_result_tapped — tracks result position and type (product/variation) for search quality measurement

Other changes:

• Removed FeatureFlag.POS_PRODUCTS_FTS and IsPosProductsFtsEnabled — FTS is now the only search path
• Removed LIKE search fallback code and related tests
• Search hint updated to always show "Search products and variations"

Test Steps

1. Open POS, go to the product list
2. Tap search and type a product name — verify results appear quickly
3. Tap a search result — verify it adds to cart
4. Check Tracks for search_results_fetched with search_method: fts
5. Check Tracks for pos_search_result_tapped with correct result_position
6. Force a full sync — check Tracks for fts_index_built with sync_type: full

Images/gif

N/A

• I have considered if this change warrants release notes and have added them to RELEASE-NOTES.txt if necessary. Use the "[Internal]" label for non-user-facing changes.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce Android by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce Android
	Platform	📱 Mobile
	Flavor	Jalapeno
	Build Type	Debug
	Build Number	734
	Version	24.3-rc-3
	Application ID	com.woocommerce.android.prealpha
	Commit	2f3a9ed
	Installation URL	7jm7433v3tpdg

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 48.27586% with 60 lines in your changes missing coverage. Please review.
✅ Project coverage is 39.55%. Comparing base (ecb8a65) to head (2f3a9ed).
⚠️ Report is 340 commits behind head on trunk.

Files with missing lines	Patch %	Lines
...d/ui/woopos/util/analytics/WooPosAnalyticsEvent.kt	0.00%	36 Missing ⚠️
...i/woopos/localcatalog/WooPosFileBasedSyncAction.kt	46.66%	6 Missing and 2 partials ⚠️
...os/home/items/products/WooPosProductsDataSource.kt	40.00%	5 Missing and 1 partial ⚠️
...android/ui/woopos/localcatalog/WooPosSyncAction.kt	33.33%	5 Missing and 1 partial ⚠️
...os/home/items/search/WooPosItemsSearchViewModel.kt	88.23%	0 Missing and 2 partials ⚠️
...items/search/WooPosProductsSearchInDbDataSource.kt	84.61%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##              trunk   #15484      +/-   ##
============================================
- Coverage     39.55%   39.55%   -0.01%     
+ Complexity    11235    11233       -2     
============================================
  Files          2252     2251       -1     
  Lines        129662   129723      +61     
  Branches      18165    18163       -2     
============================================
+ Hits          51290    51306      +16     
- Misses        73134    73180      +46     
+ Partials       5238     5237       -1     

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[samiuelson]

LGTM