feat(prompts): add prompts loader and configuration management

- Implemented a new prompts loader in `loader.go` to manage prompt templates and configurations.
- Introduced caching mechanism for prompt configurations to optimize loading.
- Added functions to apply platform-specific prompt template overrides.
- Created unit tests in `loader_test.go` to validate prompt configuration loading and reloading behavior.
- Ensured that the last valid configuration is retained in case of errors during reload.

server/internal/tenant/app/monitoring_service_date_test.go

@@ -65,3 +65,31 @@ func TestEncodeMonitoringProjectionRebuildEnvelopePreservesBusinessDate(t *testi
 	require.NoError(t, err)
 	assert.Equal(t, "2026-04-12", envelope.BusinessDate)
 }
+
+func TestFilterMonitoringPlatformsReturnsSelectedPlatform(t *testing.T) {
+	platforms := []monitoringPlatformMetadata{
+		{ID: "deepseek", Name: "DeepSeek"},
+		{ID: "qwen", Name: "通义千问"},
+		{ID: "doubao", Name: "豆包"},
+	}
+	selected := "qwen"
+
+	filtered := filterMonitoringPlatforms(platforms, &selected)
+
+	assert.Equal(t, []monitoringPlatformMetadata{
+		{ID: "qwen", Name: "通义千问"},
+	}, filtered)
+}
+
+func TestFilterMonitoringPlatformsFallsBackToDisplayName(t *testing.T) {
+	platforms := []monitoringPlatformMetadata{
+		{ID: "deepseek", Name: "DeepSeek"},
+	}
+	selected := "doubao"
+
+	filtered := filterMonitoringPlatforms(platforms, &selected)
+
+	assert.Equal(t, []monitoringPlatformMetadata{
+		{ID: "doubao", Name: "豆包"},
+	}, filtered)
+}