fix(secrets): composite keyset for group-secret admin list pagination

`list_meta` orders by `(name, environment_scope)` — a group secret name
can carry several env-scoped rows — but the cursor encoded only `name`
and paginated with `name > $cursor`. When a name's scopes straddled a
page boundary, the remaining scope rows were silently skipped from the
admin listing. Switch to a composite `(name, environment_scope)` keyset
(base64url of `name \x1f scope`) and a Postgres row-comparison predicate.
App secrets (single `*` scope per name) were unaffected; group secrets
with multi-scope names now page completely. Found in final branch review.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/manager-core/src/secrets_repo.rs

@@ -183,6 +183,27 @@ pub(crate) fn decode_cursor(cursor: &str) -> Result<String, SecretsRepoError> {
     String::from_utf8(bytes).map_err(|_| SecretsRepoError::InvalidCursor)
 }
 
+/// `list_meta` orders by `(name, environment_scope)` — a name can now have
+/// several env-scoped rows (group secrets) — so its keyset cursor must carry
+/// BOTH columns, else a name whose scopes straddle a page boundary loses its
+/// tail. Encoded as base64url of `name \x1f scope` (US is not a valid env or
+/// secret-name char, so it's an unambiguous delimiter).
+const CURSOR_SEP: char = '\u{1f}';
+
+fn encode_meta_cursor(name: &str, scope: &str) -> String {
+    URL_SAFE_NO_PAD.encode(format!("{name}{CURSOR_SEP}{scope}").as_bytes())
+}
+
+fn decode_meta_cursor(cursor: &str) -> Result<(String, String), SecretsRepoError> {
+    let bytes = URL_SAFE_NO_PAD
+        .decode(cursor)
+        .map_err(|_| SecretsRepoError::InvalidCursor)?;
+    let s = String::from_utf8(bytes).map_err(|_| SecretsRepoError::InvalidCursor)?;
+    s.split_once(CURSOR_SEP)
+        .map(|(n, sc)| (n.to_string(), sc.to_string()))
+        .ok_or(SecretsRepoError::InvalidCursor)
+}
+
 /// `(owner_column, owner_uuid)` for binding an owner into a query.
 fn owner_bind(owner: SecretOwner) -> (&'static str, Uuid) {
     match owner {
@@ -361,20 +382,27 @@ impl SecretsRepo for PostgresSecretsRepo {
         limit: u32,
     ) -> Result<SecretsMetaPage, SecretsRepoError> {
         let limit = clamp_limit(limit);
-        let last_name = match cursor {
-            Some(c) => Some(decode_cursor(c)?),
+        // Composite keyset on (name, environment_scope) — see encode_meta_cursor.
+        let last = match cursor {
+            Some(c) => Some(decode_meta_cursor(c)?),
             None => None,
         };
+        let (last_name, last_scope) = match &last {
+            Some((n, sc)) => (Some(n.as_str()), Some(sc.as_str())),
+            None => (None, None),
+        };
         let take = i64::from(limit) + 1;
         let (col, id) = owner_bind(owner);
         let sql = format!(
             "SELECT name, environment_scope, updated_at FROM secrets \
-             WHERE {col} = $1 AND ($2::text IS NULL OR name > $2) \
-             ORDER BY name ASC, environment_scope ASC LIMIT $3"
+             WHERE {col} = $1 \
+               AND ($2::text IS NULL OR (name, environment_scope) > ($2, $3)) \
+             ORDER BY name ASC, environment_scope ASC LIMIT $4"
         );
         let rows: Vec<(String, String, DateTime<Utc>)> = sqlx::query_as(&sql)
             .bind(id)
-            .bind(last_name.as_deref())
+            .bind(last_name)
+            .bind(last_scope)
             .bind(take)
             .fetch_all(&self.pool)
             .await?;
@@ -389,7 +417,9 @@ impl SecretsRepo for PostgresSecretsRepo {
             .collect();
         let next_cursor = if items.len() > limit as usize {
             items.truncate(limit as usize);
-            items.last().map(|m| encode_cursor(&m.name))
+            items
+                .last()
+                .map(|m| encode_meta_cursor(&m.name, &m.environment_scope))
         } else {
             None
         };