Downgrade styled-components to v5 for TypeScript compatibility

- Downgrade styled-components from v6.1.1 to v5.3.11
- Add @types/styled-components for v5 type definitions
- Simplify styled.ts export (v5 uses default export)
- Remove tsconfig skipLibCheck workaround (not needed with v5)
- Add string-replace-loader dependency for webpack
- Update @pezkuwi/dev to 0.85.4 (includes rollup config export fix)

This fixes TS2742 declaration emit errors that prevented npm
package builds while allowing Chrome/Firefox extension bundles.

packages/extension-ui/tsconfig.build.json

@@ -3,9 +3,7 @@
   "compilerOptions": {
     "baseUrl": "..",
     "outDir": "./build",
-    "rootDir": "./src",
-    // Required for styled-components v6 declaration emission compatibility
-    "skipLibCheck": true
+    "rootDir": "./src"
   },
   "exclude": [
     "**/*.spec.ts"