docs: define analytics rate-limit states

DESIGN.md

@@ -1,7 +1,7 @@
 # Design System — ZarinPal Merchant Analytics
 
 - Status: Draft baseline for approval
-- Version: 0.1.8
+- Version: 0.1.9
 - Last updated: 2026-08-20
 - Direction: Persian-first RTL
 
@@ -101,6 +101,7 @@ Navigation labels should describe merchant tasks, not internal database concepts
 - **Filter bar:** URL-backed state, explicit apply/reset behavior, and approved daily, weekly, Jalali-month, and Persian-season periods with unambiguous comparison baselines.
 - **Status badge:** text plus icon/shape; color reinforces but never carries meaning alone.
 - **Feedback:** inline field errors, page-level error boundary, skeleton only when layout is known, retry action for recoverable failures.
+- **Rate-limited state:** explain when an analytics start, stream, or manual retry is temporarily limited; preserve ready content, honor the server `Retry-After`, and never run a client-side retry loop.
 
 ## Data visualization
 
@@ -144,6 +145,7 @@ Navigation labels should describe merchant tasks, not internal database concepts
 
 | Version | Date | Decision |
 |---|---|---|
+| 0.1.9 | 2026-08-20 | Added rate-limit UX, 15-second SSE heartbeat/recovery, one-hour replay, and failed-section-only manual retry. |
 | 0.1.8 | 2026-08-20 | Fixed the four parallel section ids, 30-day cache, idempotent start/SSE flow, and section timeout/retry behavior. |
 | 0.1.7 | 2026-08-20 | Moved analytics results to high-TTL Redis and defined partial, parallel section delivery through authenticated SSE. |
 | 0.1.6 | 2026-08-20 | Replaced time-based analytics freshness with lazy first-access calculation and revision-based merchant/cohort cache states; defined Saturday–Friday weeks. |