Feat/send all missed posts button

[yashranaway]

Fixes #1814

Previous PR #1955

What

Added a "Resend all" button to the customer drawer that allows sellers to resend all missed posts to a customer with a single click. The button appears when there are 2+ missed posts and processes emails asynchronously via a background job.

**Flow **

• Job retrieves missed posts at execution time (not request time) to ensure up-to-date list
• Job respects 8-hour throttling mechanism using Rails.cache.fetch (same as single post sends)
• Added POST /posts/send_all_for_purchase/:purchase_id endpoint
• Created SendAllMissedPostsJob Sidekiq job
• Updated PurchasePolicy for authorization

Why

Saves time and improves UX by allowing bulk resend of missed posts.

Tests

• Controller enqueues job with seller and purchase IDs only ✓
• Job retrieves missed posts at execution time ✓
• Job respects 8-hour throttling mechanism ✓
• Job handles errors gracefully and continues processing ✓
• Authorization and eligibility checks ✓
• All tests pass ✓

Demo

Screen.Recording.2025-11-09.at.11.03.34.AM.mov

AI disclosure

I used Claude 4.5 via Cursor. All code and tests were manually verified and fixed where needed.

[yashranaway]

@EmCousin mentioned since you already have the context 🙏