docs: limit analytics reporting periods

docs/decisions/0010-limit-reporting-periods.md

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+# ADR 0010: Limit MVP reporting periods
+
+- Status: Accepted
+- Date: 2026-08-20
+
+## Context
+
+Earlier drafts included named Iranian holidays and analytical event windows. That scope adds calendar sourcing, versioning, UX distinctions, and analytics definitions that are not required for the challenge MVP.
+
+## Decision
+
+Limit reporting periods to Tehran-local daily, weekly, Jalali-month, and Persian-season views. Remove named holidays, Nowruz-specific periods, public-holiday calendars, and generic event-window reporting from the current product and data model.
+
+The exact weekly boundary remains an explicit reporting-period decision; it must not be inferred differently by the database, API, and frontend.
+
+## Consequences
+
+- No holiday/event entities, imported holiday snapshots, runtime calendar API, or holiday-specific UI are required.
+- A reporting-date dimension remains useful for deterministic Gregorian/Jalali conversion and consistent week, month, and season grouping.
+- Holiday/event analytics may return only through a future approved spec and ADR.