deploy: P2-17 install.ps1 (Windows installer)

Pwsh installer that detects arch, downloads
$Server/agent/binary?os=windows&arch=amd64 to
C:\Program Files\restic-manager\, runs the agent in -enroll-server
[+ -enroll-token] mode (token flow OR announce-and-approve), then
calls 'restic-manager-agent install' to register the SCM service.
Surfaces existing scheduled tasks named *restic* without disabling.

CLAUDE.md restage block updated to also stage install.ps1 alongside
install.sh.

CLAUDE.md

@@ -43,6 +43,8 @@ cp bin/restic-manager-agent \
    /tmp/rm-smoke/data/agent-binaries/restic-manager-agent-linux-amd64
 cp deploy/install/install.sh \
    /tmp/rm-smoke/data/install/install.sh
+cp deploy/install/install.ps1 \
+   /tmp/rm-smoke/data/install/install.ps1
 cp deploy/install/restic-manager-agent.service \
    /tmp/rm-smoke/data/install/restic-manager-agent.service