M12b: category contract v2 on the server (schema 2, fourteen defaults, finer import mapping)

- migrations/0002_categories_v2.sql, byte-identical to contracts/schema/migrations/0002_categories_v2.sql
  (SPEC §14.1.1), with an identity test; SCHEMA_VERSION = 2 (E-1 reports it, the importer's check follows).
- Seed test on a fresh database (the fourteen rows of AC-7.2, server_version 11 to 14) and an upgrade test of a
  v1 database in use (0001 applied through the migrator, then users, a custom, a renamed and an archived default,
  an account, a recurring template, expenses): every earlier row unchanged, the four rows above the old
  sequence, foreign_key_check empty, schema_version 2, a pull from the old cursor returns exactly the four rows.
- DefaultCategoryKey with the fourteen keys (wire enum and contracts/openapi.yaml); icons 33 and colours 14
  (§9.7) in validation.
- The two category examples M12a held back (E-26 response-default, sync/pull-page-categories-v2) and its
  contracts-check patch for them and the enum.
- Importer: splitwise_categories.csv per the §10.8 v0.8 table (D-053), DEFAULT_KEYS of fourteen, synthetic
  fixtures for the finer mapping (Insurance/Försäkringar to insurance among them), a schema-1 refusal test.
- Test harnesses seed users at server_version 15/16 (after the fourteen seeds); pull counts 10 -> 14.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQd3pEP9UeN2uifbHknQ7B

server/crates/kvitt-server/tests/skeleton/support.rs

@@ -62,13 +62,26 @@ pub struct TestApp {
 impl TestApp {
     /// A migrated, empty database (no users).
     pub async fn empty() -> Self {
+        Self::migrated_to(None).await
+    }
+
+    /// An empty database at schema version 1: only `0001_init.sql` applied, through the server's own migrator, so a
+    /// later `db::migrate` upgrades it the way a deployed v1 database is upgraded.
+    pub async fn at_v1() -> Self {
+        Self::migrated_to(Some(1)).await
+    }
+
+    async fn migrated_to(target: Option<i64>) -> Self {
         let dir = TempDir::new();
         let config = Config::from_lookup(|k| {
             (k == "KVITT_DATA_DIR").then(|| dir.0.to_string_lossy().into_owned())
         })
         .unwrap();
         let pool = db::connect(&config.database_path()).await.unwrap();
-        db::migrate(&pool).await.unwrap();
+        match target {
+            Some(version) => db::MIGRATOR.run_to(version, &pool).await.unwrap(),
+            None => db::migrate(&pool).await.unwrap(),
+        }
         let clock = FixedClock::new(parse_ts(NOW).unwrap());
         let state = AppState::new(config, pool).with_clock(Arc::new(clock.clone()));
         Self {
@@ -81,10 +94,17 @@ impl TestApp {
     /// Admin and member users, one device each, plus a revoked device of the member.
     pub async fn household() -> Self {
         let app = Self::empty().await;
-        let pool = &app.state.db;
+        app.seed_household().await;
+        app
+    }
+
+    /// Inserts the users and devices of [`TestApp::household`] (users at `server_version` 15 and 16, after the
+    /// fourteen seeded categories; the sequence is not advanced).
+    pub async fn seed_household(&self) {
+        let pool = &self.state.db;
         for (id, role, name, version) in [
-            (ADMIN_ID, "admin", "Jacob", 11),
-            (MEMBER_ID, "member", "Partner", 12),
+            (ADMIN_ID, "admin", "Jacob", 15),
+            (MEMBER_ID, "member", "Partner", 16),
         ] {
             sqlx::query(
                 "INSERT INTO users (id, role, display_name, picture_version, created_at, updated_at, server_version) \
@@ -122,7 +142,6 @@ impl TestApp {
             .await
             .unwrap();
         }
-        app
     }
 
     pub async fn send(&self, request: Request<Body>) -> Reply {