Add Linux development station role with systemd services for code-server and OpenCode

- Implemented handlers for restarting code-server and OpenCode services.
- Created main tasks for setting up a Linux development station, including user management, package installation, and configuration.
- Added validation for OpenCode server credentials and code-server password.
- Introduced tool package management for npm, uv, and go installers.
- Developed templates for systemd service units for code-server and OpenCode.
- Included scripts for starting code-server and OpenCode with SSH agent support.
- Updated inventory and Terraform configuration to include new development host.

ansible/roles/linux_dev_station/templates/ssh-agent-start.sh.j2

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+
+# SSH agent starter — idempotent, safe to source from concurrent sessions.
+# Starts ssh-agent if not already running, then adds keys.
+
+export SSH_AUTH_SOCK="{{ linux_dev_station_ssh_agent_socket }}"
+
+# Start ssh-agent if socket doesn't exist
+if [ ! -S "$SSH_AUTH_SOCK" ]; then
+  eval "$(/usr/bin/ssh-agent -a "{{ linux_dev_station_ssh_agent_socket }}" -s)" > /dev/null 2>&1
+fi
+
+# Wait for the agent socket to appear
+__wait=0
+while [ ! -S "$SSH_AUTH_SOCK" ] && [ "$__wait" -lt 15 ]; do
+  sleep 1
+  __wait=$(( __wait + 1 ))
+done
+
+# Add keys if the agent is running but has none loaded
+if [ -S "$SSH_AUTH_SOCK" ]; then
+  if ssh-add -l 2>/dev/null | grep -q "The agent has no identities"; then
+    for _key in {{ linux_dev_station_ssh_agent_keys | map('quote') | join(' ') }}; do
+      if [ -f "$_key" ]; then
+        if [ -n "{{ linux_dev_station_ssh_agent_passphrase }}" ]; then
+          printf '%s\n' "{{ linux_dev_station_ssh_agent_passphrase }}" | ssh-add "$_key" 2>/dev/null || true
+        else
+          ssh-add "$_key" 2>/dev/null || true
+        fi
+      fi
+    done
+  fi
+fi