fix(migrations): replace hardcoded schema strings with MigrationConstants.SchemaName

Two migration files had literal schema strings that were missed in earlier passes:
- cv-search-data AddJobSearchTables: two CreateIndex calls used "cvSearch"
- rag-data InitialRagSchema: FK principalSchema used "rag"

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

Apis/cv-search-data/Migrations/20260522093356_AddJobSearchTables.cs

@@ -73,13 +73,13 @@ namespace CvSearch.Data.Migrations
 
             migrationBuilder.CreateIndex(
                 name: "IX_JobSearchResults_SessionId",
-                schema: "cvSearch",
+                schema: MigrationConstants.SchemaName,
                 table: "JobSearchResults",
                 column: "SessionId");
 
             migrationBuilder.CreateIndex(
                 name: "IX_JobSearchSessions_Status",
-                schema: "cvSearch",
+                schema: MigrationConstants.SchemaName,
                 table: "JobSearchSessions",
                 column: "Status");
         }