Set version to 0.0.1 and pin assembly identity for CI builds

The release and nightly workflows stamp a date-based version into
build.yaml (1.0.20260729.42). That build segment exceeds the 16-bit
limit AssemblyVersion and FileVersion require, so it would fail the
compile with CS7034 if it reached them.

Directory.Build.targets is imported after Directory.Build.props and is
not rewritten by CI, so pinning the assembly identity there keeps those
builds working. The manifest version is untouched - Jellyfin identifies
plugins by GUID plus manifest version, not assembly version. Verified by
building with a date-based version injected.

Directory.Build.props

@@ -1,7 +1,7 @@
 <Project>
     <PropertyGroup>
-        <Version>0.0.0.0</Version>
+        <Version>0.0.1.0</Version>
-        <AssemblyVersion>0.0.0.0</AssemblyVersion>
+        <AssemblyVersion>0.0.1.0</AssemblyVersion>
-        <FileVersion>0.0.0.0</FileVersion>
+        <FileVersion>0.0.1.0</FileVersion>
     </PropertyGroup>
 </Project>

Directory.Build.targets

@@ -0,0 +1,16 @@
+<Project>
+  <!--
+    The CI workflows stamp a date-based version into build.yaml (e.g. 1.0.20260729.42). The build
+    segment (20260729) exceeds the 16-bit limit (0-65535) that AssemblyVersion and FileVersion
+    require, which fails the compile with CS7034/CS7035 if it ever reaches those properties.
+
+    Directory.Build.targets is imported after the project and after Directory.Build.props, and no
+    workflow rewrites it, so pinning valid assembly identities here keeps the build safe. Only the
+    .NET assembly identity is normalised; the plugin manifest version is unaffected, and Jellyfin
+    identifies plugins by GUID plus manifest version rather than by assembly version.
+  -->
+  <PropertyGroup>
+    <AssemblyVersion>1.0.0.0</AssemblyVersion>
+    <FileVersion>1.0.0.0</FileVersion>
+  </PropertyGroup>
+</Project>

build.yaml

@@ -1,7 +1,7 @@
 ---
 name: "Watched Together"
 guid: "aa3288a0-e8c1-43e2-8045-8c3411142a5b"
-version: "1.0.0.0"
+version: "0.0.1.0"
 targetAbi: "10.11.0.0"
 framework: "net9.0"
 overview: "One shared login for several people; watched state flows back to each member's own account"