refactor+feat: Snapshot-Router-Split + generischer ChecklistAgent + AGB-Modul

- Item 2: Snapshot-Doc-Checks (cookie/impressum/dse/agb) in snapshot_check_routes.py
  (agent_compliance_check_routes.py 464→365 Z.); gleiche Pfade, in main.py registriert.
- ChecklistAgent-Basis: DSE-Logik generalisiert (L1/L2, kurze Titel, _severity_
  override-Hook). DSEAgent + AGBAgent sind jetzt Thin-Subclasses → künftige
  Doc-Agenten (widerruf/avv/…) trivial.
- Item 4: AGBAgent (§§ 305 ff. BGB, AGB_CHECKLIST) + agb-check + AGB-Tab via
  AgentModuleTab. Kein Library-Firehose.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend-compliance/compliance/services/specialist_agents/agb/__init__.py

@@ -0,0 +1,5 @@
+"""AGB-Agent — Allgemeine Geschäftsbedingungen (§§ 305 ff. BGB), kuratiert."""
+
+from .agent import AGBAgent
+
+__all__ = ["AGBAgent"]

backend-compliance/compliance/services/specialist_agents/agb/agent.py

@@ -0,0 +1,19 @@
+"""AGBAgent — Allgemeine Geschäftsbedingungen (§§ 305 ff. BGB).
+
+Thin-Subclass von ChecklistAgent über die kuratierte AGB_CHECKLIST (L1
+Pflichtangaben + L2 Detailchecks). KEIN Library-Firehose.
+"""
+
+from __future__ import annotations
+
+from compliance.services.doc_checks.agb_checks import AGB_CHECKLIST
+
+from .._checklist_agent import ChecklistAgent
+
+
+class AGBAgent(ChecklistAgent):
+    CHECKLIST = AGB_CHECKLIST
+    agent_id = "agb"
+    agent_version = "1.0"
+    doc_type = "agb"
+    owned_mc_ids = tuple(c["id"] for c in AGB_CHECKLIST)