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>

blueprints/scheduled_messages/models.py

@@ -0,0 +1,37 @@
+import enum
+
+from tortoise import fields
+from tortoise.models import Model
+
+
+class MessageChannel(enum.Enum):
+    IMESSAGE = "imessage"
+    EMAIL = "email"
+
+
+class MessageStatus(enum.Enum):
+    PENDING = "pending"
+    SENT = "sent"
+    FAILED = "failed"
+    CANCELLED = "cancelled"
+
+
+class ScheduledMessage(Model):
+    id = fields.UUIDField(primary_key=True)
+    recipient = fields.CharField(max_length=255)
+    channel = fields.CharEnumField(enum_type=MessageChannel, max_length=10)
+    content = fields.TextField()
+    subject = fields.CharField(max_length=255, null=True)
+    scheduled_at = fields.DatetimeField()
+    status = fields.CharEnumField(
+        enum_type=MessageStatus, max_length=10, default=MessageStatus.PENDING
+    )
+    error_message = fields.TextField(null=True)
+    created_by = fields.ForeignKeyField(
+        "models.User", related_name="scheduled_messages"
+    )
+    created_at = fields.DatetimeField(auto_now_add=True)
+    updated_at = fields.DatetimeField(auto_now=True)
+
+    class Meta:
+        table = "scheduled_messages"