chore: normalize line endings (CRLF -> LF)

No content changes: git diff --ignore-all-space over these files is empty.
The churn came from editing on Windows against a repo checked out with LF.

backend/pfm-web-app/postcss.config.mjs

@@ -1,7 +1,7 @@
-const config = {
-  plugins: {
-    "@tailwindcss/postcss": {},
-  },
-};
-
-export default config;
+const config = {
+  plugins: {
+    "@tailwindcss/postcss": {},
+  },
+};
+
+export default config;