Improve mise setup task

Use declarative approach to set working directory

mise.toml

@@ -3,5 +3,12 @@ LAST_FM_USER = 'change-me'
 LAST_FM_API_KEY = 'change-me'
 OPENAI_KEY = 'change-me'
 
+[tasks.npm-install]
+run = 'npm install'
+hide = true
+dir = 'assets'
+
 [tasks.setup]
-run = ['cd assets && npm install', 'mix setup']
+depends = ['npm-install']
+description = 'Install dependencies and setup the database'
+run = ['mix setup']