chore: add prettier and format all files

- Install prettier ^3.6.2
- Add .prettierrc with project formatting rules
- Add .prettierignore to exclude generated files and dependencies
- Add npm scripts: format and format:check
- Format all files with prettier

.github/renovate.json

@@ -1,6 +1,4 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "extends": [
-    "github>ivuorinen/renovate-config"
-  ]
+  "extends": ["github>ivuorinen/renovate-config"]
 }