feat: add windows-rdp-keepalive module

Author: Youngthug38

modules/windows-rdp-keepalive/README.md

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+# Windows RDP Keep Alive
+
+This module runs a background script on Windows workspaces that detects active RDP sessions and prevents the workspace from shutting down due to inactivity.
+
+## Usage
+
+```hcl
+module "rdp_keepalive" {
+  source   = "[registry.coder.com/modules/windows-rdp-keepalive/coder](https://registry.coder.com/modules/windows-rdp-keepalive/coder)"
+  version  = "1.0.0"
+  agent_id = coder_agent.main.id
+}

modules/windows-rdp-keepalive/main.tf

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+terraform {
+  required_version = ">= 1.0"
+  required_providers {
+    coder = {
+      source  = "coder/coder"
+      version = ">= 0.12"
+    }
+  }
+}
+
+variable "agent_id" {
+  description = "The ID of the Coder agent."
+  type        = string
+}
+
+variable "interval" {
+  description = "Interval in seconds to check for RDP connections."
+  type        = number
+  default     = 60
+}
+
+resource "coder_script" "rdp_keepalive" {
+  agent_id     = var.agent_id
+  display_name = "RDP Keep Alive"
+  icon         = "/icon/remote-desktop.svg"
+  run_on_start = true
+  
+  # We run a PowerShell loop in the background
+  script = <<EOT
+$Interval = ${var.interval}
+
+Write-Host "Starting RDP Keep Alive Monitor..."
+
+while ($true) {
+    # check for active RDP-Tcp sessions
+    $rdpSession = query user | Select-String "rdp-tcp" | Select-String "Active"
+    
+    if ($rdpSession) {
+        # RDP is active. We need to generate 'activity' to prevent shutdown.
+        # Since Coder monitors network/ssh, the simplest way to bump activity 
+        # is to simulate a state change or write to stdout which the agent captures.
+        
+        $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
+        Write-Host "[$timestamp] RDP Active - Sending KeepAlive signal"
+        
+        # This subtle output to the agent's log is often enough to reset the "idleness" timer
+        # because the PTY receives data.
+    }
+    
+    Start-Sleep -Seconds $Interval
+}
+EOT
+}