feat(cv-matcher): add AiPrompts table; remove MyAiDbContext dependency

cv-matcher-data:
- Add AiPromptEntity (Key, Language, Value, Description, UpdatedAt)
- Add AiPrompts DbSet to CvMatcherDbContext with composite PK
- Migration AddAiPrompts: create cvMatcher.AiPrompts table and seed
  ai.cv-match.system-prompt (language "*") with the current prompt value

cv-matcher-api:
- Add IAiPromptsRepository / EfAiPromptsRepository under Data/Repositories/
- CvMatcherService: inject IAiPromptsRepository; replace _templates.Render(...)
  with async DB lookup + simple string replacement
- Program.cs: register IAiPromptsRepository (scoped); remove MyAiDbContext,
  ITemplateService/DbTemplateService registrations and MyAiDbContext migration call
- Remove myai-data ProjectReference

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

Apis/cv-matcher-data/CvMatcherDbContext.cs

@@ -14,6 +14,7 @@ public sealed class CvMatcherDbContext : DbContext
 
     public DbSet<CvMatchResultEntity> CvMatchResults => Set<CvMatchResultEntity>();
     public DbSet<CvMatcherChatCacheEntity> CvMatcherChatCache => Set<CvMatcherChatCacheEntity>();
+    public DbSet<AiPromptEntity> AiPrompts => Set<AiPromptEntity>();
 
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
@@ -41,5 +42,16 @@ public sealed class CvMatcherDbContext : DbContext
             entity.Property(x => x.ResponseText).IsRequired();
             entity.Property(x => x.CreatedAt).HasDefaultValueSql("SYSUTCDATETIME()");
         });
+
+        modelBuilder.Entity<AiPromptEntity>(entity =>
+        {
+            entity.ToTable("AiPrompts");
+            entity.HasKey(x => new { x.Key, x.Language });
+            entity.Property(x => x.Key).HasMaxLength(128);
+            entity.Property(x => x.Language).HasMaxLength(8);
+            entity.Property(x => x.Value).IsRequired();
+            entity.Property(x => x.Description).HasMaxLength(500).HasDefaultValue(string.Empty);
+            entity.Property(x => x.UpdatedAt).HasDefaultValueSql("SYSUTCDATETIME()");
+        });
     }
 }