🧹 Resolve Security Vulnerabilities and Migrate Paraglide to v2

[MFA-X-AI]

Noticed some security warnings in our package audit and realized they were tied to a few libraries that hadn't been updated in a while. Since one of the main culprits was actually deprecated, I attempted to clean up the stack. I also took the opportunity to fix a breaking issue in our CI pipeline related to pyAV dependency builds.

The stuff this PR did:

• Cleaned up the audit: I cleared out the current warnings. Most were fixed with standard updates (Vite, Vitest), but I added two small overrides for ajv and cookie since those nested versions are currently stuck upstream.
• Migrated Paraglide: The high-severity risks were coming from the old @inlang/paraglide-sveltekit. I updated it with the now recommended paraglide-js (v2).
• Simplified the architecture: I was able to delete the old <ParaglideJS> layout wrapper and the i18n.ts file. It's now using the newer middleware and native SvelteKit reroute hooks.
• Fixed CI Pipeline Dependency Builds: The GitHub Actions workflow was failing because the av package was attempting to compile from source against an incompatible version of FFmpeg in the ubuntu-latest runner. I added an apt-get install -y ffmpeg step to provide the base system media libraries, and added an av!=14.4.0 constraint to pyproject.toml. This forces uv to download a pre-compiled wheel instead, which bypasses the C-compiler entirely, turns the pipeline green.

The project is now passing pnpm audit and the test suite is running successfully.