style(core): apply cargo fmt across routes, services, models, tests

Pure rustfmt reflow (import grouping, array/match-arm/call-arg wrapping,
alphabetized module decls, comment realignment). No semantic change:
full-diff and `git diff -w` both confirm logic byte-identical to 271c363;
workspace builds and all 74 core tests pass. Retained pre-existing WIP
brought forward after verification.

tests/integration_test.rs

@@ -294,7 +294,12 @@ async fn test_sbc_rejects_duplicate_cards() {
         .as_str()
         .unwrap()
         .to_string();
-    let (s, _) = json_post(&app, &format!("/packs/open/{pack_id}"), serde_json::json!({})).await;
+    let (s, _) = json_post(
+        &app,
+        &format!("/packs/open/{pack_id}"),
+        serde_json::json!({}),
+    )
+    .await;
     assert_eq!(s, StatusCode::OK);
 
     let (_, coll) = json_get(&app, "/collection").await;
@@ -312,9 +317,16 @@ async fn test_sbc_rejects_duplicate_cards() {
         }),
     )
     .await;
-    assert_eq!(s, StatusCode::BAD_REQUEST, "duplicate submission must be rejected: {result}");
+    assert_eq!(
+        s,
+        StatusCode::BAD_REQUEST,
+        "duplicate submission must be rejected: {result}"
+    );
     assert!(
-        result["error"].as_str().unwrap_or_default().contains("duplicate"),
+        result["error"]
+            .as_str()
+            .unwrap_or_default()
+            .contains("duplicate"),
         "expected a duplicate-card error, got: {result}"
     );
 }