refactor(gateway): split data-plane files into egress/supervisor/git_gate services

Group the gateway's data-plane modules into three service sub-packages
mirroring the host-side trio (bot_bottle.egress / .supervisor / .git_gate):

  gateway/egress/     addon_core, addon, dlp_config, dlp_detectors
  gateway/supervisor/ server            (was supervise_server)
  gateway/git_gate/   render, http_backend

Prefix-stripped filenames now that the package namespaces them; each
sub-package has a thin docstring __init__ (no eager imports, cheap leaf
loads). The two cross-cutting files stay at the gateway root:
policy_resolver (shared per-client lookup) and gateway_init, renamed to
bootstrap now that gateway/ already namespaces it.

Updated all importers (bot_bottle + tests), the in-VM/container `-m`
launch strings, the Dockerfile.gateway addon shim + ENTRYPOINT, and the
five gateway entries in scripts/critical-modules.txt. Full unit suite
green (2243).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_egress_addon_core.py

@@ -12,7 +12,7 @@ import unittest
 from pathlib import Path
 from urllib.parse import urlsplit
 
-from bot_bottle.gateway.egress_addon_core import (
+from bot_bottle.gateway.egress.addon_core import (
     LOG_BLOCKS,
     LOG_FULL,
     LOG_OFF,
@@ -1377,15 +1377,15 @@ class TestScanOutboundEnhanced(unittest.TestCase):
 
 class TestOutboundDetectorNames(unittest.TestCase):
     def test_entropy_in_outbound_detector_names(self):
-        from bot_bottle.gateway.egress_addon_core import OUTBOUND_DETECTOR_NAMES
+        from bot_bottle.gateway.egress.addon_core import OUTBOUND_DETECTOR_NAMES
         self.assertIn("entropy", OUTBOUND_DETECTOR_NAMES)
 
     def test_known_secrets_in_outbound_detector_names(self):
-        from bot_bottle.gateway.egress_addon_core import OUTBOUND_DETECTOR_NAMES
+        from bot_bottle.gateway.egress.addon_core import OUTBOUND_DETECTOR_NAMES
         self.assertIn("known_secrets", OUTBOUND_DETECTOR_NAMES)
 
     def test_token_patterns_in_outbound_detector_names(self):
-        from bot_bottle.gateway.egress_addon_core import OUTBOUND_DETECTOR_NAMES
+        from bot_bottle.gateway.egress.addon_core import OUTBOUND_DETECTOR_NAMES
         self.assertIn("token_patterns", OUTBOUND_DETECTOR_NAMES)