Add scheduled messages and strip markdown from iMessage responses

Strip markdown formatting (bold, italic, headers, code, links, lists) from
LLM responses before sending via iMessage. Add scheduled messages feature
with CRUD API, background scheduler loop, and admin frontend panel.

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

app.py

@@ -15,6 +15,7 @@ import blueprints.rag
 import blueprints.users
 import blueprints.whatsapp
 import blueprints.imessage
+import blueprints.scheduled_messages
 import blueprints.users.models
 from config.db import TORTOISE_CONFIG
 
@@ -52,6 +53,7 @@ app.register_blueprint(blueprints.email.email_blueprint)
 app.register_blueprint(blueprints.rag.rag_blueprint)
 app.register_blueprint(blueprints.whatsapp.whatsapp_blueprint)
 app.register_blueprint(blueprints.imessage.imessage_blueprint)
+app.register_blueprint(blueprints.scheduled_messages.scheduled_messages_blueprint)
 
 
 async def _obsidian_sync_loop():
@@ -86,8 +88,13 @@ async def lifespan():
     if os.getenv("OBSIDIAN_CONTINUOUS_SYNC") == "true":
         watcher_task = asyncio.create_task(_obsidian_sync_loop())
 
+    from blueprints.scheduled_messages.scheduler import scheduled_messages_loop
+
+    scheduler_task = asyncio.create_task(scheduled_messages_loop())
+
     yield
 
+    scheduler_task.cancel()
     if watcher_task is not None:
         watcher_task.cancel()