fix: Configure EF Core migration history tables with schema-qualified names

Each DbContext now explicitly configures its migration history table to use
the schema-qualified name pattern [schemaName].[_Migrations]:
- [cvMatcher].[_Migrations] for CvMatcherDbContext
- [emailApi].[_Migrations] for EmailApiDbContext
- [cvSearch].[_Migrations] for CvSearchDbContext
- [rag].[_Migrations] for RagDbContext
- [myAi].[_Migrations] for MyAiDbContext

This is done via OnConfiguring() with UseSqlServer().MigrationsHistoryTable(name, schema).

Removed incorrect rename migrations that were created due to misunderstanding
of the proper EF Core configuration approach.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Apis/rag-data/RagDbContext.cs

@@ -17,6 +17,13 @@ public sealed class RagDbContext : DbContext
     public DbSet<RagEmbeddingCacheEntity> RagEmbeddingCache => Set<RagEmbeddingCacheEntity>();
     public DbSet<RagChatCompletionCacheEntity> RagChatCompletionCache => Set<RagChatCompletionCacheEntity>();
 
+    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+    {
+        base.OnConfiguring(optionsBuilder);
+        // Configure migration history table to use schema-qualified name: [rag].[_Migrations]
+        optionsBuilder.UseSqlServer(x => x.MigrationsHistoryTable(MigrationTableName, SchemaName));
+    }
+
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
         modelBuilder.HasDefaultSchema(SchemaName);