feat: add acronym matching for directories (#1002)

[Erio-Harrison]

Description

This PR implements acronym matching for directory names as requested in #1002.
Users can now query directories like /home/user/hooli-interactive-computer-keyboard
using their acronym hick. The filter_by_keywords method first attempts regular
substring matching, falling back to match_acronym if needed.

Changes

• Modified filter_by_keywords in src/db/stream.rs to integrate acronym matching.
• Added match_acronym to generate acronyms from directory basenames.
• Supports separators: -, _, , ..
• Case-insensitive matching via to_lowercase.

Testing

• Verified with test cases:
  • ["hick"] matches /home/bachman/Documents/hooli-interactive-computer-keyboard.
  • ["HICK"] matches (case-insensitive).
  • ["hick"] fails for /home/bachman/Documents/hooli-interactive-keyboard (incomplete acronym).
  • ["abc"] matches /home/bachman/Documents/a-b-c.

Closes #1002