feat(security): dedicated install flags decouple git_url/pip from security_level

Install via git URL and pip install are no longer gated by
security_level. Each surface gets a dedicated config.ini flag —
allow_git_url_install / allow_pip_install (both default false, secure
by default) — that fully REPLACES the security-level term for these two
features. The network-position invariant is retained: a non-local
listener stays denied regardless of the flags unless
network_mode = personal_cloud.

- New pure predicate is_dedicated_install_allowed() in
  common/manager_security (no config access; callers resolve config)
- Legacy endpoints /v2/customnode/install/git_url and .../pip switch
  from is_allowed_security_level('high+') to the flag gate; batch
  installs of unknown git URLs likewise (middle+ entry gate unchanged,
  unknown-pip 'block' stays unconditional; response shapes preserved)
- Config readers/writers (glob + legacy) parse and persist the flags;
  denial logs and frontend 403 messages name the responsible flag and
  note the non-local-listener requirement (network_mode=personal_cloud)
- No auto-seed from security_level — users previously on weak/normal-
  must opt in explicitly (see CHANGELOG migration notes; README
  documents the new contract)
- Update the pre-existing permissive E2E harness
  (start_comfyui_permissive.sh + test_e2e_legacy_real_ops.py) to the
  new contract: it now also sets allow_git_url_install /
  allow_pip_install = true, since security_level = normal- alone no
  longer opens the git_url/pip endpoints

Tests: predicate truth table proving security_level independence in
both directions, dual-reader config contract, security-level-matrix
freeze guards, legacy gate regression guards (121 unit), plus 22
real-server E2E tests incl. URL-form pip install with self-clean.

comfyui_manager/common/manager_security.py

@@ -83,6 +83,25 @@ def is_loopback(address):
         return False
 
 
+def is_dedicated_install_allowed(flag_value: bool, listen_address: str, network_mode: str) -> bool:
+    """P-direct predicate for the dedicated install flags (goal265-spec.md §1.2).
+
+    allowed iff flag AND (loopback listener OR network_mode == 'personal_cloud').
+
+    Gates the git-URL / standalone-pip install surfaces via the dedicated
+    ``allow_git_url_install`` / ``allow_pip_install`` config flags, fully
+    decoupled from ``security_level`` (REPLACE, not AND — spec §1.1 inv. 1).
+    The network-position term retains today's invariant that a public
+    (non-loopback, non-personal_cloud) listener stays denied regardless of
+    the flags (spec §1.1 inv. 2).
+
+    Pure function — NO config access; callers resolve ``flag_value`` and
+    ``network_mode`` through their own config reader and pass values in
+    (preserves common/ layering: this module must stay config-import-free).
+    """
+    return bool(flag_value) and (is_loopback(listen_address) or network_mode.lower() == 'personal_cloud')
+
+
 def do_nothing():
     pass