Resolves issue #13

- Switched model to bge-small-en-v1.5
- Added lazy re-embedding
- Added model version tracking per vector
- Added conversion of vectors to the new model

internal/vector/sqlitevec/client_test.go

@@ -38,7 +38,8 @@ func testDB(t *testing.T) (*sql.DB, func()) {
 			doc_type TEXT,
 			field_type TEXT,
 			project TEXT,
-			scope TEXT
+			scope TEXT,
+			model_version TEXT
 		)
 	`)
 	require.NoError(t, err)