fix: update test config for session_secret removal and Arc master key

Remove session_secret field (no longer in AppConfig), wrap
master_encryption_key in Arc<String>, and pass a generated job_id
to db::syntheses::create which now requires it.

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

backend/tests/common/mod.rs

@@ -107,8 +107,7 @@ impl TestApp {
         // Build a test config with bypassed external services
         let config = AppConfig {
             database_url: test_db_url,
-            session_secret: "a".repeat(64),
-            master_encryption_key: "ab".repeat(32), // 64 hex chars
+            master_encryption_key: std::sync::Arc::new("ab".repeat(32)), // 64 hex chars
             app_url: "http://localhost:3000".into(),
             port: 0,
             static_dir: "/tmp/ai_synth_test_static".into(), // not used in API tests
@@ -430,7 +429,7 @@ impl TestApp {
         week: &str,
         sections_json: &serde_json::Value,
     ) -> uuid::Uuid {
-        let row = db::syntheses::create(&self.pool, user_id, week, sections_json)
+        let row = db::syntheses::create(&self.pool, user_id, week, sections_json, uuid::Uuid::new_v4())
             .await
             .expect("Failed to insert test synthesis");
         row.id