Add pnpm-lock.yaml and stop gitignoring it so CI passes

The CI (ci.yml) and test (test.yml) workflows use `cache: pnpm` and
`pnpm install --frozen-lockfile`, both of which require a committed
pnpm-lock.yaml. The repo declared `packageManager: pnpm@10.6.5` but
.gitignore excluded the lockfile, so the workflows failed at the
setup-node step with "Dependencies lock file is not found".

- Remove pnpm-lock.yaml from .gitignore
- Commit the lockfile generated with pnpm 10.6.5

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ralyodio

.gitignore

@@ -8,7 +8,6 @@ yarn-debug.log*
 yarn-error.log*
 .pnpm-debug.log*
 
-pnpm-lock.yaml
 ffmpeg_build/
 
 # Environment variables