⚡ Bolt: Optimize FirstAidRepository search and database seeding

[NITISH-R-G]

💡 What:

• Introduced a strongly typed _FirstAidEntry model for the corpus that parses raw JSON once.
• Pre-computed and cached lowercased string fields (titleLower, tagsLower, searchHaystackLower) within _FirstAidEntry.
• Refactored ensureInitialized() to use appDb.executeBatch for SQLite initialization instead of repeatedly calling appDb.execute in a for loop.

🎯 Why:

• Calling .toLowerCase() and accessing string keys on dynamic maps (Map<String, dynamic>) inside high-frequency search and autocomplete loops (_lookupTokenScore, getSuggestions) is very inefficient, especially when scaling the corpus size.
• Using a loop of appDb.execute queries creates an N+1 performance bottleneck that blocks the UI and slows down first-launch or initialization.

📊 Impact:

• Significantly reduces memory allocation overhead and CPU time during keystroke search/autocomplete.
• Much faster database seeding by leveraging SQLite batch execution.

🔬 Measurement:

• Verified by checking search functionality and database initialization performance. Tests successfully compile and pass.

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PR created automatically by Jules for task 966680841653860509 started by @NITISH-R-G

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