feat: align Publisher dashboard shell and favicon fallbacks

[ShenzheZhu]

Summary

• align the Publisher navbar to the Writer portal's full-width viewport padding
• add the Writer-style left sidebar shell to the /tasks dashboard only
• preserve the existing centered layout for task creation and detail routes
• add ICO and PNG favicon fallbacks and mirror the Writer metadata declarations

Behavior

Before, the Publisher header used a constrained container while the dashboard content followed a different alignment model, and browser requests for /favicon.ico had no matching asset. After this change, the Publisher dashboard follows the same shell geometry as Writer while nested routes remain unchanged, and browser tabs can resolve ICO, PNG, or SVG icons.

Verification

• pnpm --filter @humanly/frontend type-check
• pnpm --filter @humanly/frontend build
• git diff --cached --check
• verified Publisher favicon ICO/PNG hashes match the Writer assets

Closes #1023