feat(byok): add model selection to BYOK settings panel and overlay custom model on route resolution

memento-note/lib/byok.ts

@@ -51,12 +51,12 @@ export async function getActiveByokKey(userId: string, provider: string) {
 export async function resolveByokApiKey(
   userId: string,
   providerType: string,
-): Promise<{ plaintext: string; provider: string } | null> {
+): Promise<{ plaintext: string; provider: string; model: string | null } | null> {
   const row = await getActiveByokKey(userId, providerType);
   if (!row) return null;
   try {
     const plaintext = await decryptApiKey(row.encryptedKey);
-    return { plaintext, provider: row.provider };
+    return { plaintext, provider: row.provider, model: row.model };
   } catch (err) {
     console.error('[byok] Failed to decrypt key for provider', providerType, err);
     return null;
@@ -67,16 +67,17 @@ export async function applyByokToConfig(
   billingUserId: string,
   providerType: string,
   config: Record<string, string>,
-): Promise<{ config: Record<string, string>; usedByok: boolean }> {
+): Promise<{ config: Record<string, string>; usedByok: boolean; model: string | null }> {
   const byok = await resolveByokApiKey(billingUserId, providerType);
-  if (!byok) return { config, usedByok: false };
+  if (!byok) return { config, usedByok: false, model: null };
 
   const { apiKeyConfigKey } = getProviderConfigKeys(providerType);
-  if (!apiKeyConfigKey) return { config, usedByok: false };
+  if (!apiKeyConfigKey) return { config, usedByok: false, model: null };
 
   return {
     config: { ...config, [apiKeyConfigKey]: byok.plaintext },
     usedByok: true,
+    model: byok.model,
   };
 }