Decide guest grants explicitly instead of by permission name

guest_grantable_permissions() opened any permission whose name ended
'.view' or '.read' to the guest role, on the reasoning that reading is
the safe default. That is true of a permission gating a list of asset
numbers and false of one gating bytes, and a suffix cannot tell them
apart. Twenty-four of eighty-five qualified and none had been decided:

  applications.view  reached the SYSTEM-context PowerShell bodies and
                     the installer binaries pushed to bays
  backups.view       returned the full payload that the separate
                     backups.download permission exists to protect
  assets.view        gated a global search that queries the staff
                     directory, USB history and network inventory with
                     no per-domain check of its own
  audit.view         usernames, addresses, the before/after of every
  settings.view      change, and every setting row - both admin
                     category, opened by naming alone
  users.view         gates nothing at all; list_users is
                     require_role('admin')

Every entry is now declared, by CORE_GUEST_GRANTABLE or by the plugin
that owns the permission, having read what its routes actually return.
Adding one is a code change, which is the point: it puts the decision
in a diff rather than in a suffix.

The two routes serving script bodies and installer packages move to a
new applications.download permission, which is not grantable, so a site
can still open the catalogue metadata to its floor without the bytes
going with it.

The declared set preserves the grants this site had already chosen:
applications.view, computers.view, endpoints.view, reports.view,
tools.secrets, warranty.view.

Two known gaps are recorded on the hooks that expose them rather than
silently carried: the computer serializer publishes every column plus
resolved rdp:// and vnc:// links, and the per-asset endpoint panels are
keyed on a small integer so walking ids reconstructs much of the roster
that endpoints.fleet exists to protect. Neither is widened here.

A shipped test was granting guests audit.view and passing.

Scope: product
(cherry picked from commit 347402896c)

plugins/warranty/plugin.py

@@ -174,5 +174,13 @@ class WarrantyPlugin(BasePlugin):
             ('warranty.delete', 'Delete warranties', 'warranty'),
         ]
 
+    def get_guest_grantable_permissions(self) -> List[str]:
+        """Coverage dates and vendor for an asset somebody is standing at.
+
+        Nothing here is a credential and nothing reaches a supplier portal; the
+        provider lookups run server-side with keys the caller never sees.
+        """
+        return ['warranty.view']
+
     def init_app(self, app: Flask, db_instance) -> None:
         logger.info(f"Warranty plugin initialized (v{self.meta.version})")