feat(tools): add SQLite to PostgreSQL migration tool

Existing installs hold their whole library in jellyfin.db, so switching to the
PostgreSQL provider needs a one-shot data move.

- add Jellyfin.DbMigrator reading SQLite tables and bulk-writing them to PostgreSQL
- validate table names against the source schema before generating SQL
- upload a pre-migration copy of the SQLite file to S3 when S3_BACKUP_BUCKET is set
- emit a per-table row-count report and support a dry-run mode

Directory.Packages.props

@@ -8,6 +8,7 @@
     <PackageVersion Include="AutoFixture.AutoMoq" Version="4.18.1" />
     <PackageVersion Include="AutoFixture.Xunit3" Version="4.19.0" />
     <PackageVersion Include="AutoFixture" Version="4.18.1" />
+    <PackageVersion Include="AWSSDK.S3" Version="4.0.103.1" />
     <PackageVersion Include="BDInfo" Version="0.8.0" />
     <PackageVersion Include="BitFaster.Caching" Version="2.6.1" />
     <PackageVersion Include="BlurHashSharp.SkiaSharp" Version="1.4.0-pre.1" />