fix: make FTS5 optional for template search (fixes Claude Desktop compatibility)

- Added runtime FTS5 detection in database adapters
- Removed FTS5 from required schema to prevent "no such module" errors
- FTS5 tables/triggers created conditionally only if supported
- Template search automatically falls back to LIKE when FTS5 unavailable
- Works in ALL SQLite environments (Claude Desktop, restricted envs, etc.)

This ensures search_templates() works correctly regardless of SQLite build,
while still providing optimal performance when FTS5 is available.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/database/schema.sql

@@ -47,7 +47,5 @@ CREATE INDEX IF NOT EXISTS idx_template_nodes ON templates(nodes_used);
 CREATE INDEX IF NOT EXISTS idx_template_updated ON templates(updated_at);
 CREATE INDEX IF NOT EXISTS idx_template_name ON templates(name);
 
--- Full-text search for templates
-CREATE VIRTUAL TABLE IF NOT EXISTS templates_fts USING fts5(
-  name, description, content=templates
-);
+-- Note: FTS5 tables are created conditionally at runtime if FTS5 is supported
+-- See template-repository.ts initializeFTS5() method