Notification upgrades: lifecycle, configurable levels, summaries

- NOTIFY_LEVELS chooses which event levels are sent (default trade,error).
- NOTIFY_LIFECYCLE sends explicit start/stop messages; the kill switch always
  notifies at error level.
- SUMMARY_INTERVAL_MINUTES sends a periodic portfolio summary (equity, per
  strategy P&L, allocation, halted state) via a background task started with
  the run and stopped on stop/kill/shutdown.
- Wires the new vars plus the go-live vars through both compose files and the
  deploy workflow. Adds tests.

backend/app/config.py

@@ -60,6 +60,13 @@ class Settings(BaseSettings):
     telegram_bot_token: str = ""
     telegram_chat_id: str = ""
     notify_webhook_url: str = ""
+    # Event levels to notify on. Defaults to trades and errors; add "info" to
+    # include start/stop messages, or "warning" for blocked entries.
+    notify_levels: str = "trade,error"
+    # Explicit start/stop lifecycle messages (separate from event levels).
+    notify_lifecycle: bool = True
+    # Periodic portfolio summary, in minutes (0 disables).
+    summary_interval_minutes: int = 0
 
     # Optional bearer token required on /api requests (defense-in-depth behind
     # the Traefik Basic auth). Empty disables the check.
@@ -80,6 +87,10 @@ class Settings(BaseSettings):
     def cors_origin_list(self) -> list[str]:
         return [origin.strip() for origin in self.cors_origins.split(",") if origin.strip()]
 
+    @property
+    def notify_level_set(self) -> set[str]:
+        return {level.strip().lower() for level in self.notify_levels.split(",") if level.strip()}
+
     @property
     def is_live(self) -> bool:
         return self.mode == "live"