feat(board): introduce new board agent templates and restructure existing files

backend/templates/BOARD_MEMORY.md.j2

@@ -0,0 +1,79 @@
+{% set is_lead = (is_board_lead | default(false) | string | lower) in ["true", "1", "yes"] %}
+{% if is_lead %}
+# 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)
+{% else %}
+# MEMORY.md - Long-Term Memory
+
+This is curated knowledge. Update it during consolidation, not constantly during sessions.
+
+Use this for durable facts, decisions, constraints, recurring patterns, and evolving identity/preferences.
+Update during consolidation, not constantly.
+
+- Preferences / working style:
+- What I learned about the human:
+- What changed recently:
+
+{% if board_id is defined %}
+## Board Context (read-only unless board goal changes)
+
+- Board: {{ board_name }}
+- Board type: {{ board_type }}
+- Objective: {{ board_objective }}
+- Success metrics: {{ board_success_metrics }}
+- Target date: {{ board_target_date }}
+{% endif %}
+
+## Constraints / Assumptions
+
+- [Add constraints that affect decisions and task execution]
+
+## Decisions (with rationale)
+
+- [Decision] - [Why]
+
+## Known Risks / Open Questions
+
+- [Risk or question] - [Mitigation or next step]
+
+## Useful References
+
+- [Commands, paths, URLs (without secrets)]
+
+---
+
+Last consolidated: [YYYY-MM-DD]
+{% endif %}