perf(search): prefix-by-default Deployments and config-audit search; bounded Contains opt-in (ScadaBridge#50)

Deployments free-text search and the config-audit EntityName filter no longer
emit LIKE '%term%' by default. Prefix (LIKE 'term%') is the default; substring
is an explicit opt-in (DeploymentSearchMode.Contains / entityNameContains)
always bounded by a DeployedAt/Timestamp window (explicit, else 30 days).
Migration PrefixSearchIndexes adds DeployedBy, RevisionHash and EntityName
indexes. Deployments page gains a 'Match anywhere' checkbox.

Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV

tests/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests/DeploymentListQueryRepositoryTests.cs

@@ -258,7 +258,7 @@ public class DeploymentListQueryRepositoryTests : IDisposable
     /// <param name="expected">The expected.</param>
     /// <returns>A task that represents the asynchronous operation.</returns>
     [Theory]
-    [InlineData("Filler", "dep-a")]     // instance unique name
+    [InlineData("Line3", "dep-a")]      // instance unique name (prefix)
     [InlineData("dep-b", "dep-b")]      // deployment id
     [InlineData("carol", "dep-b")]      // initiating user
     [InlineData("rev-a", "dep-a")]      // revision hash