Add VM connectivity troubleshooting and HTTP workaround

VM cannot connect via HTTPS due to self-signed certificate errors.

Added:
- test-vm-connectivity.ps1: 5-step diagnostic for VM
- agent/QUICK-FIX-VM.md: Use HTTP for Hyper-V local network
- open-firewall-for-vm.ps1: Open Windows Firewall

Since VM and host are on same physical machine (Hyper-V internal
network), HTTP is acceptable for local monitoring.

For production: Use proper TLS certificates.

agent/QUICK-FIX-VM.md

@@ -0,0 +1,51 @@
+# Quick Fix: Agent Can't Connect from VM
+
+## Problem
+SSL certificate errors when connecting from VM to host.
+
+## Solution: Use HTTP on Local Network
+
+Since the VM and host are on a trusted local network (Hyper-V), use HTTP instead of HTTPS.
+
+### On VM - Set HTTP in Registry:
+
+```powershell
+# On VM (as Administrator):
+New-Item -Path 'HKLM:\SOFTWARE\GE\ShopDB' -Force
+Set-ItemProperty -Path 'HKLM:\SOFTWARE\GE\ShopDB' -Name 'BaseUrl' -Value 'http://172.31.96.1:5001'
+Set-ItemProperty -Path 'HKLM:\SOFTWARE\GE\ShopDB' -Name 'CollectorKey' -Value 'shopdb_pat_b4a3fe2a01abc6bc1cb685280e65a8c35d52ec43'
+```
+
+### Test it works:
+
+```powershell
+# On VM:
+curl.exe http://172.31.96.1:5001
+# Should return HTML
+```
+
+### Then run the agent:
+
+```powershell
+cd C:\ProgramData\ShopDB\EndpointAgent
+.\shopdb-endpoint-agent.exe --once
+```
+
+## Why HTTP is OK Here
+
+- ✅ VM and host on same physical machine (Hyper-V)
+- ✅ Traffic never leaves the host
+- ✅ Hyper-V internal network is isolated
+- ✅ No external network exposure
+
+For production multi-machine deployment, use HTTPS with proper certificates.
+
+## Alternative: Fix HTTPS (More Complex)
+
+If you need HTTPS:
+
+1. Export the self-signed cert from host
+2. Import to VM's Trusted Root Certification Authorities
+3. Use HTTPS URL
+
+See main INSTALL-ON-VM.md for details.