feat(backend): default verify_tls to false for lab/redteam Mythic

flip default to False at model, API fallback, adapter, and factory layers.
add migration 0008 flipping c2_config.verify_tls server_default to false.
suppress urllib3 InsecureRequestWarning when verify_tls is off.
adapt c2 tests to new verify_tls default.

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

backend/app/services/c2/mythic.py

@@ -15,6 +15,8 @@ from __future__ import annotations
 from datetime import datetime
 
 import requests
+import urllib3
+from urllib3.exceptions import InsecureRequestWarning
 
 from backend.app.services.c2.adapter import (
     C2Adapter,
@@ -113,10 +115,14 @@ query GetTaskOutput($display_id: Int!) {
 class MythicAdapter(C2Adapter):
     """Real Mythic 3.x adapter using GraphQL over HTTP."""
 
-    def __init__(self, url: str, api_token: str, verify_tls: bool = True) -> None:
+    def __init__(self, url: str, api_token: str, verify_tls: bool = False) -> None:
         self._url = url.rstrip("/") + "/graphql"
         self._token = api_token
         self._verify = verify_tls
+        if not verify_tls:
+            # Lab/red-team Mythic instances commonly use self-signed certs.
+            # Suppress urllib3 warnings once per process when verification is off.
+            urllib3.disable_warnings(InsecureRequestWarning)
 
     def _headers(self) -> dict[str, str]:
         return {