Clean up build warnings: MF DTS, autoprefixer color-adjust, dev CORS

Three non-fatal warnings surfaced by the Jenkins build log, fixed in
the config layer:

- module-federation.config.ts: dts: false. The @module-federation/
  dts-plugin fails under our strict tsconfig and logs TYPE-001 every
  build. Remote types are not needed at runtime; consumers generate
  their own via their dev toolchain.

- src/styles/_layout.scss: color-adjust → print-color-adjust. The
  unprefixed color-adjust shorthand is deprecated; the standard name
  is print-color-adjust. Matches the -webkit- prefixed sibling.

- modern.config.ts: tools.devServer.headers explicitly set. MF warns
  when devServer.headers is empty and auto-assigns '*'. Providing an
  explicit allowlist silences the banner in dev builds; production
  behavior is unaffected (real reverse proxy manages CORS).

module-federation.config.ts

@@ -12,4 +12,10 @@ export default createModuleFederationConfig({
     react: { singleton: true, requiredVersion: "^18.2.0" },
     "react-dom": { singleton: true, requiredVersion: "^18.2.0" },
   },
+  // Disable DTS generation at build time. @module-federation/dts-plugin@2.3.3
+  // fails against our strict tsconfig (exactOptionalPropertyTypes +
+  // noUncheckedIndexedAccess) and logs a TYPE-001 error. Types for the
+  // exposed modules are shipped to consumers via their own dev-time
+  // toolchain; the runtime does not need them.
+  dts: false,
 });