Admit kiosk callers by network position, not only by device token

The device token assumes a handful of fixed screens an administrator
provisions once. That is not how these kiosks are used: most people open the
page on their own PC, and there is no login, so per-browser provisioning would
mean touching every PC on the floor and losing it again on the next reimage or
cleared profile. A screen in that state did not look refused either - the USB
kiosk rendered a working page whose every call answered 404.

Both kiosks now admit a caller on either ground, the same shape the GE-Enforce
client endpoints already use: the per-device token, or a source address inside
an allowlist. Wall screens keep the token and are not confined to the
allowlist; everyone else is admitted by where they are on the network. Still
gated on the site's enable flag, so nothing opens by itself, and both
allowlists ship empty - token-only until a site enters its ranges.

- shopdb.api gains ip_in_cidrs and request_ip_allowlisted (contract 0.35.0).
  On the surface because both plugins need the identical gate, and a CIDR
  parser copied into two of them is where a fail-open creeps in later. They
  fail closed on an empty setting, an unparseable caller address and a
  malformed entry, and they read remote_addr rather than raw X-Forwarded-For -
  so the IIS rewrite rule is what makes them meaningful, which the module says
  at length.
- Separate settings per kiosk, usb_kiosk_allowed_cidrs and
  printedparts_kiosk_allowed_cidrs. One must not grant the other, for the same
  reason the tokens are separate.
- Both settings pages get a picker listing the network plugin's subnets with
  their VLANs. It stores resolved CIDR strings, not subnet ids: the setting has
  to work at a site that does not run that plugin and must not break when an
  inventory row is deleted. Entries matching no subnet are shown rather than
  hidden, since a stale one left by an inventory edit looks exactly like a
  hand-typed range.
- USBKiosk says it was not admitted instead of pretending to work, which
  PartsKiosk already did.
- The USB settings page keyed text-vs-boolean off the token alone. Adding a
  second text setting to the boolean path would have saved it as the word
  'true' - the bug that replaced the kiosk token and 404'd every provisioned
  screen. Both load and save now key off a list, with a spec on it.

The trade, stated plainly in the admin UI: anyone on an allowed network can
check a drive in or out against a badge number they guess, and the record
carries that person's name. Badges are attribution, not authorization. Keeping
the ranges narrow is what bounds it; login is the alternative and was ruled out
because these users do not sign in.

plugins/usb/plugin.py

@@ -150,6 +150,22 @@ class USBPlugin(BasePlugin):
                                'kiosk once as /usb-kiosk?token=<value> on each '
                                'screen',
             },
+            {
+                'key': 'usb_kiosk_allowed_cidrs',
+                'value': '',
+                'valuetype': 'string',
+                'category': 'usb',
+                'description': 'Networks allowed to use the kiosk WITHOUT the '
+                               'device token, as comma-separated CIDRs (for '
+                               'example 192.0.2.0/24). For people who open '
+                               'the kiosk on their own PC and never log in - '
+                               'provisioning a token into every browser is not '
+                               'workable. Empty = token only. Wall screens keep '
+                               'using the token either way. Requires the IIS '
+                               'X-Forwarded-For rewrite rule to be live, or the '
+                               'app sees the proxy address and this matches '
+                               'nothing.',
+            },
             {
                 'key': 'usb_kiosk_allow_return_for_others',
                 'value': 'true',