Add auto memory distillation scheduler (APScheduler)

- scheduler.py: AsyncIOScheduler with three cron jobs
    short  daily     03:00 (no LLM, always fast)
    mid    weekly    Sun 03:30 (LLM)
    long   monthly   1st 04:00 (LLM — off by default)
- config.py: AUTO_DISTILL, AUTO_DISTILL_SHORT/MID/LONG .env flags
- main.py: start/stop scheduler in FastAPI lifespan
- routers/distill.py: GET /distill/status — next run times + config
- requirements.txt: apscheduler>=3.10
- HELP.md: updated planned items, added /distill/status to API table

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

cortex/config.py

@@ -26,6 +26,13 @@ class Settings(BaseSettings):
     nextcloud_talk_bot_secret: str = ""   # set in .env
     nextcloud_talk_timeout: int = 55
 
+    # Auto-distillation schedule — override in .env
+    # AUTO_DISTILL=false disables entirely
+    auto_distill: bool = True
+    auto_distill_short: bool = True   # daily at 03:00 — rolls session logs → MEMORY_SHORT
+    auto_distill_mid: bool = True     # weekly Sunday at 03:30 — LLM summarizes short → mid
+    auto_distill_long: bool = False   # monthly 1st at 04:00 — off by default (manual review recommended)
+
     # Memory tier token budgets — soft caps used during distillation
     # Override in .env: MEMORY_BUDGET_LONG=4000 etc.
     memory_budget_long: int = 2000