feat: Phase 1 — delta temporel + decay news + cycle_meta dans prompts IA

- database.py: get_last_completed_cycle_ts() pour mesurer le delta entre cycles
- auto_cycle.py: calcul delta_minutes + cycle_meta dict transmis aux fonctions IA
- ai_analyzer.py: apply_news_decay() (halflife par catégorie), partition_news_by_age()
  (3 buckets: inter_cycle / recent_24h / older), _build_temporal_news_block() pour
  le prompt suggestion; cycle_meta injecté aussi dans score_patterns_with_context()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/services/database.py

@@ -1212,6 +1212,16 @@ def reset_journal_history():
     conn.close()
 
 
+def get_last_completed_cycle_ts() -> Optional[str]:
+    """Return ISO timestamp of the last successfully completed cycle, or None."""
+    conn = get_conn()
+    row = conn.execute(
+        "SELECT completed_at FROM cycle_runs WHERE status='completed' ORDER BY completed_at DESC LIMIT 1"
+    ).fetchone()
+    conn.close()
+    return row["completed_at"] if row else None
+
+
 def add_cycle_run(run_id: str, trigger: str = "auto") -> None:
     conn = get_conn()
     conn.execute(