Separate Prettier and ESLint according to best practices (#9565)

* Separate Prettier and ESLint according to best practices

- Create standalone .prettierrc configuration file
- Remove eslint-plugin-prettier integration from ESLint config
- Replace with eslint-config-prettier to disable conflicting rules
- Remove eslint-plugin-prettier dependency
- Add dedicated format and format:check scripts
- Update lint-staged to run Prettier and ESLint separately
- Format entire codebase with new Prettier configuration

This follows the recommended approach from Prettier documentation:
https://prettier.io/docs/integrating-with-linters#notes

* Remove test comment

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Co-authored-by: codegen-sh[bot] <131295404+codegen-sh[bot]@users.noreply.github.com>

app.json

@@ -3,13 +3,7 @@
   "description": "Open source wiki and knowledge base for growing teams",
   "website": "https://www.getoutline.com/",
   "repository": "https://github.com/outline/outline",
-  "keywords": [
-    "wiki",
-    "team",
-    "node",
-    "markdown",
-    "slack"
-  ],
+  "keywords": ["wiki", "team", "node", "markdown", "slack"],
   "success_url": "/",
   "formation": {
     "web": {
@@ -222,4 +216,4 @@
       "required": false
     }
   }
-}
+}