feat(memory): update MEMORY.md structure and consolidate identity preferences

backend/templates/LEAD_MEMORY.md

@@ -0,0 +1,35 @@
+# MEMORY.md
+
+Durable facts and decisions only.
+No daily logs. No secrets.
+
+## Current Delivery Status
+
+### Objective
+(TODO)
+
+### Current State
+- State: Working | Blocked | Waiting | Done
+- Last updated: (YYYY-MM-DD HH:MM {{ user_timezone or "UTC" }})
+
+### Plan (3-7 steps)
+1. (TODO)
+2. (TODO)
+
+### Last Progress
+- (TODO)
+
+### Next Step (exactly one)
+- (TODO)
+
+### Blocker (if any)
+- (TODO)
+
+### Evidence
+- (TODO)
+
+## Durable decisions
+- YYYY-MM-DD: (decision) — (rationale)
+
+## Reusable playbooks
+- (TODO)