refactor: rename egress-proxy → egress everywhere

The manifest key is `egress:` now; finish the rename so the rest of
the codebase matches. Files (Dockerfile.egress, claude_bottle/egress.py
etc.), classes (Egress, EgressConfig, EgressRoute, EgressPlan,
DockerEgress), constants (EGRESS_HOSTNAME, EGRESS_ROUTES, ...),
container name prefix (claude-bottle-egress-*), docker network alias
(egress), the introspection host (_egress.local), the MCP tool IDs
(egress-block, list-egress-routes), and the preflight label all drop
the `-proxy` suffix.

tests/unit/test_manifest_md_load.py

@@ -31,7 +31,7 @@ _BOTTLE_DEV = """
         - host: example.com
     ---
 
-    The dev bottle. Anthropic OAuth via egress-proxy.
+    The dev bottle. Anthropic OAuth via egress.
 """
 
 _AGENT_IMPL = """