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/Entities/AiPromptEntity.cs

@@ -0,0 +1,10 @@
+namespace CvMatcher.Data.Entities;
+
+public sealed class AiPromptEntity
+{
+    public string Key { get; set; } = string.Empty;
+    public string Language { get; set; } = string.Empty;
+    public string Value { get; set; } = string.Empty;
+    public string Description { get; set; } = string.Empty;
+    public DateTime UpdatedAt { get; set; }
+}