Complete Economic Observatory MVP (ADAPTIVE-WP-0002)

Add file-based Bubble, Stripe, and OpenRouter importers; usage attribution,
cost allocation, pricing simulator, credit wallets, and recommendations in the
dashboard API. Document whynot-design UI workflow and archive the finished
workplan with all ten tasks marked done.

projects/coulomb-pricing/observatory/membership_analytics.py

@@ -0,0 +1,48 @@
+from __future__ import annotations
+
+from .models import MembershipRecord
+
+
+def _period_prefix(date: str | None) -> str | None:
+    if not date or len(date) < 7:
+        return None
+    return date[:7]
+
+
+def build_membership_analytics(
+    members: list[MembershipRecord],
+    period: str,
+    history: list[str],
+) -> dict:
+    active = sum(1 for member in members if member.status == "active")
+    new_members = sum(1 for member in members if _period_prefix(member.joined_at) == period)
+    churned = sum(1 for member in members if _period_prefix(member.churned_at) == period)
+
+    prior_period = None
+    sorted_periods = sorted(history)
+    if period in sorted_periods:
+        index = sorted_periods.index(period)
+        if index > 0:
+            prior_period = sorted_periods[index - 1]
+
+    prior_active = active
+    if prior_period:
+        prior_active = sum(
+            1
+            for member in members
+            if member.status == "active" and _period_prefix(member.joined_at) <= prior_period
+        )
+
+    growth_rate = None
+    if prior_active:
+        growth_rate = round(((active - prior_active) / prior_active) * 100, 1)
+
+    return {
+        "period": period,
+        "total_members": len(members),
+        "active_members": active,
+        "new_members": new_members,
+        "churned_members": churned,
+        "growth_rate_pct": growth_rate,
+        "snapshot_source": "membership.json",
+    }