feat(auth): sign in with Steam (MODULE_API 1.17.0)

Steam is a built-in provider beside Google and Discord (STEAM_SIGNIN.md,
D392-D396). OpenID 2.0: the assertion is verified server to server with
check_authentication, return_to must match byte for byte, and the claimed id
must be a 17-digit SteamID64. A Steam Web API key is required to enable it
(D394); persona name and avatar are stored on the identity and refreshed at
each sign-in, and a failed lookup never blocks one. Steam never signs anybody
up (D395), on the web or the mobile bridge. Several Steam accounts may be
linked; DELETE /auth/me/account/identities/:provider takes ?id= to unlink one.

MODULE_API 1.17.0: ctx.identities.list, api.onIdentityLinking (refuse-only,
fails closed, module text never shown) and api.onIdentityLinked. No unlink
hook (D393). Schema additive; OpenAPI, routes and engagement manifests
regenerated with no modules installed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/src/model/userIdentities/userIdentities.db.js

@@ -13,21 +13,45 @@ async function findByProviderSubject(provider, subject) {
 // All identities linked to a given internal user (for the Account page).
 async function listForUser(userId) {
   return query(
-    'SELECT id, provider, subject, email, created_at FROM user_identities WHERE user_id = ? ORDER BY provider',
+    `SELECT id, provider, subject, email, display_name, avatar_url, created_at
+       FROM user_identities WHERE user_id = ? ORDER BY provider, created_at`,
     [userId],
   )
 }
 
-async function insert({ userId, provider, subject, email = null }) {
+async function insert({ userId, provider, subject, email = null, displayName = null, avatarUrl = null }) {
   const res = await query(
-    'INSERT INTO user_identities (user_id, provider, subject, email) VALUES (?, ?, ?, ?)',
-    [userId, provider, subject, email],
+    `INSERT INTO user_identities (user_id, provider, subject, email, display_name, avatar_url)
+     VALUES (?, ?, ?, ?, ?, ?)`,
+    [userId, provider, subject, email, displayName, avatarUrl],
   )
   return res.insertId
 }
 
-// Remove a user's link to a provider. Returns rows deleted.
-async function deleteForUserProvider(userId, provider) {
+// Refresh the name and avatar a provider reported at sign-in (Steam, D394). Only
+// what the provider sent is written: a lookup that failed leaves the last good
+// values in place rather than blanking them.
+async function updateProfile(id, { displayName, avatarUrl }) {
+  const sets = []
+  const vals = []
+  if (displayName) { sets.push('display_name = ?'); vals.push(displayName) }
+  if (avatarUrl) { sets.push('avatar_url = ?'); vals.push(avatarUrl) }
+  if (!sets.length) return 0
+  const res = await query(`UPDATE user_identities SET ${sets.join(', ')} WHERE id = ?`, [...vals, id])
+  return Number(res.affectedRows || 0)
+}
+
+// Remove a user's link to a provider — every identity of it, or, given an
+// identity id, that one only (a user may hold several Steam accounts). Returns
+// rows deleted.
+async function deleteForUserProvider(userId, provider, identityId = null) {
+  if (identityId != null) {
+    const res = await query(
+      'DELETE FROM user_identities WHERE user_id = ? AND provider = ? AND id = ?',
+      [userId, provider, identityId],
+    )
+    return Number(res.affectedRows || 0)
+  }
   const res = await query(
     'DELETE FROM user_identities WHERE user_id = ? AND provider = ?',
     [userId, provider],
@@ -35,4 +59,4 @@ async function deleteForUserProvider(userId, provider) {
   return Number(res.affectedRows || 0)
 }
 
-module.exports = { findByProviderSubject, listForUser, insert, deleteForUserProvider }
+module.exports = { findByProviderSubject, listForUser, insert, updateProfile, deleteForUserProvider }