Keep Vulkan loader in Inno libmpv bundle

[Blackspirits]

Summary

The Windows ZIP packages copy the complete verified libmpv bundle, including vulkan-1.dll, because the current libmpv build imports the Vulkan loader at load time. The Inno installer staging still installs only libmpv-2.dll, so the installer package drops a dependency that the ZIP path preserves.

This change:

• adds vulkan-1.dll from the existing libmpv-temp verified bundle to the Inno installer
• installs it beside libmpv-2.dll in the per-user Subtitle Edit data folder
• changes exactly one installer source line and no runtime behavior

Current-base verification

• current build-ui.yml still copies all of libmpv-temp/* into the Windows ZIP and explicitly documents the Vulkan dependency
• current Subtitle_Edit_Installer.iss still stages only libmpv-2.dll
• the installer file is byte-for-byte identical to the base reviewed for internal PR Keep Vulkan loader in Inno libmpv bundle #19
• the reviewed one-line fix was therefore ported exactly onto current upstream
• current diff is one commit / one file / one added line
• full solution restore passed
• full solution build passed
• full solution test suite passed on the first run
• retry step was not used
• validation run: #34725744782
• upstream later advanced from fa6d8623c2adb0c646b6d31a11b221b855339bbe to 7dbf7e03c937241ff9511ae413d5552720249de1; those intervening commits do not touch the installer or build workflow paths relevant to this change

Base is upstream fa6d8623c2adb0c646b6d31a11b221b855339bbe.

This PR supersedes internal draft #19.

AI assistance: ChatGPT was used to independently re-audit the current libmpv packaging paths, confirm the ZIP/Inno dependency mismatch, verify exact base-file identity, and port the minimal packaging fix.