feat: scheduled reminders + less aggressive article summary

Add scheduled messages/reminders system:
- New scheduled_messages table in memory-service with CRUD endpoints
- schedule_message, list_reminders, cancel_reminder tools for the bot
- Background scheduler loop (30s) sends due reminders automatically
- Supports one-time, daily, weekly, weekdays, monthly repeat patterns

Make article URL handling non-blocking:
- Show 3 options (discuss, text summary, audio) instead of forcing audio wizard
- Default to passing article context to AI if user just keeps chatting
- New AWAITING_LANGUAGE state for cleaner audio flow FSM

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

article_summary/state.py

@@ -10,6 +10,7 @@ from enum import Enum, auto
 class ArticleState(Enum):
     IDLE = auto()
     URL_DETECTED = auto()
+    AWAITING_LANGUAGE = auto()  # Audio flow: waiting for language selection
     LANGUAGE = auto()
     DURATION = auto()
     TOPICS = auto()