feat: add user prompt to generation

- Update `Generation` model to include `userPrompt`.
- Update `GenerationService` to accept and use `userPrompt` in AI prompt.
- Update `Generation` API to accept `userPrompt`.
- Update `CreateLookDialog` to include an input for `userPrompt`.
- Add tests for `userPrompt` functionality.
- Install `dotenv` for prisma migrations.

package.json

@@ -53,6 +53,7 @@
     "@types/bun": "^1.3.8",
     "@typescript-eslint/eslint-plugin": "^8.54.0",
     "@typescript-eslint/parser": "^8.54.0",
+    "dotenv": "^17.2.4",
     "eslint": "^10.0.0",
     "eslint-config-prettier": "^10.1.8",
     "prettier": "^3.8.1",