geenforce: harden allowlist + fix share-less kiosk client and display scope

- allowlist auth uses remote_addr, not the spoofable first X-Forwarded-For hop
  (adds _trusted_client_ip + a regression test); rate-limit path unchanged
- client psm1: fix Set-StrictMode crashes reading absent keys in Get-ShopdbConfig
  (token-less mode) and Resolve-ShopdbPayloads (no-payload entries); validate
  the manifest response is JSON before overwriting the last-known-good cache
- runner: pass the engine its required -InstallerRoot/-LogFile; create the log
  directory so enforce logging is not silently lost on a fresh kiosk
- display scope: dispatcher writes an all-users Startup shortcut instead of
  Start-Process (SYSTEM cannot show a window in session 0), resolves the base
  URL from HKLM, and adds an always-on power/no-lock entry; tests updated for
  the 6-entry scope

plugins/geenforce/api/routes.py

@@ -46,18 +46,36 @@ REPORT_SCOPE = 'geenforce.report'
 ALLOWED_CIDRS_SETTING = 'geenforce_allowed_cidrs'
 
 
+def _trusted_client_ip():
+    """The trustworthy caller IP for the AUTH allowlist.
+
+    Uses request.remote_addr, NOT the raw X-Forwarded-For header. Proxies APPEND
+    to X-Forwarded-For, so its first hop is attacker-controlled: parsing it (as
+    _client_ip does for rate-limiting) would let any caller send
+    'X-Forwarded-For: <allowlisted-ip>' and bypass the token. remote_addr cannot
+    be forged here - behind IIS the URL-Rewrite rule overwrites X-Forwarded-For
+    with the real TCP peer and waitress (--trusted-proxy=127.0.0.1
+    --trusted-proxy-headers=x-forwarded-for) derives remote_addr from it; a
+    client hitting waitress directly is not a trusted proxy, so its remote_addr
+    is its own real peer address. Either way remote_addr is the true client.
+    """
+    return request.remote_addr or ''
+
+
 def _ip_allowlisted():
     """True when the caller IP falls in the configured geenforce allowlist.
 
     Lets vaulted fleet PCs reach the client endpoints without a per-PC token -
     network trust replaces the shared secret. Fails closed: an unparseable
     caller IP or malformed allowlist entry never matches. Empty setting = off.
+    Uses the SPOOF-RESISTANT remote_addr (see _trusted_client_ip), never the raw
+    X-Forwarded-For header.
     """
     raw = (Setting.get(ALLOWED_CIDRS_SETTING) or '').strip()
     if not raw:
         return False
     try:
-        ip = ipaddress.ip_address(_client_ip())
+        ip = ipaddress.ip_address(_trusted_client_ip())
     except ValueError:
         return False
     for part in raw.split(','):