feat(ai): IEmbeddingProvider foundation (#18)

src/InboxIntel.Infrastructure/DependencyInjection.cs

@@ -67,13 +67,23 @@ public static class DependencyInjection
         services.AddHttpClient("ollama");
         services.AddHttpClient("openai");
 
-        // AI provider selected by configured mode.
+        // AI provider selected by configured mode. Embeddings come from Ollama when local,
+        // otherwise the Null provider (empty vectors) so semantic features degrade to lexical.
         var aiMode = config.GetSection(AiOptions.SectionName).GetValue<AiProviderMode>("Mode");
         switch (aiMode)
         {
-            case AiProviderMode.LocalOllama: services.AddScoped<IAiProvider, OllamaProvider>(); break;
-            case AiProviderMode.CloudOpenAi: services.AddScoped<IAiProvider, OpenAiProvider>(); break;
-            default: services.AddScoped<IAiProvider, NullAiProvider>(); break;
+            case AiProviderMode.LocalOllama:
+                services.AddScoped<IAiProvider, OllamaProvider>();
+                services.AddScoped<IEmbeddingProvider, OllamaEmbeddingProvider>();
+                break;
+            case AiProviderMode.CloudOpenAi:
+                services.AddScoped<IAiProvider, OpenAiProvider>();
+                services.AddScoped<IEmbeddingProvider, NullEmbeddingProvider>(); // OpenAI embeddings: future
+                break;
+            default:
+                services.AddScoped<IAiProvider, NullAiProvider>();
+                services.AddScoped<IEmbeddingProvider, NullEmbeddingProvider>();
+                break;
         }
         services.AddScoped<IAiService, AiService>();