[WIP] Improves relevance scoring of search terms

[tompollard]

This PR makes some changes the search algorithm:

1. Updates pre-processing of search terms:

   • Case normalization (e.g., "MIMIC-IV" matches "mimic-iv")
   • Whitespace normalization

2. Improves relevance scoring:

   • Higher weight for exact matches (e.g., "MIMIC-IV" matches "MIMIC-IV" more strongly than "MIMIC")
   • Prioritizes title matches (e.g., "MIMIC" in title ranks higher than in description)

Also adds tests.