ci(release): retry-sign-release waits 3h for SignPath approval, like release.yml (#1795)

## Why

`retry-sign-release.yml` waits only **3600 s** for the SignPath `release-signing` approval, while `release.yml` waits **10800 s** (since 4ee7b10). The v0.72.0 retry ([run 40409167558](https://github.com/smart-mcp-proxy/mcpproxy-go/actions/runs/40409167558)) timed out after 1h01 on both arches with the requests still `WaitingForApproval`, so a re-dispatch gives the approver a third of the window the original run has.

## Change

One line: `wait-for-completion-timeout-in-seconds: 3600 → 10800` in the retry workflow. The job has no `timeout-minutes`, so GitHub's 6h default still covers download + signing + upload.

No code change; workflow_dispatch only.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: Dumbris

.github/workflows/retry-sign-release.yml

@@ -82,7 +82,7 @@ jobs:
           artifact-configuration-slug: 'initial'
           github-artifact-id: '${{ steps.reupload.outputs.artifact-id }}'
           wait-for-completion: true
-          wait-for-completion-timeout-in-seconds: 3600
+          wait-for-completion-timeout-in-seconds: 10800
           output-artifact-directory: signed
 
       - name: Prepare signed installer