Extend campaign planner with platform-aware post composition: optional
title (YouTube/TikTok/Reddit/Pinterest), mediaUrls attachments, and
per-platform settings overrides merged into Postiz __type. New
platform-specs.ts library encodes platform constraints. Bump asset
cache version to v=3.
Campaigns dashboard now sends Authorization headers on flow fetch/create
and surfaces 401/403 with a clear message instead of silently failing.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
