chore: ignore default database path

Database default will be "db" and will commonly be created at project root during testing.

Signed-off-by: Ophestra Umiker <cat@ophivana.moe>

.gitignore

@@ -6,6 +6,9 @@
 *.dylib
 /backend
 
+# database
+/db
+
 # Test binary, built with `go test -c`
 *.test