Fix procedure_stats plan query to use DECOMPRESS after compression migration

PR #433 migrated procedure_stats to compressed LOB storage but missed
updating GetProcedureStatsPlanXmlByCollectionIdAsync — it still referenced
the old query_plan column instead of DECOMPRESS(query_plan_text). This
would cause plan viewing to fail for procedure stats rows.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: erikdarlingdata

Dashboard/Services/DatabaseService.QueryPerformance.cs

@@ -2409,7 +2409,7 @@ FROM collect.query_store_data AS qsd
         SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
 
         SELECT
-            ps.query_plan
+            CAST(DECOMPRESS(ps.query_plan_text) AS nvarchar(max)) AS query_plan_text
         FROM collect.procedure_stats AS ps
         WHERE ps.collection_id = @collection_id;";