fix(GRO-574): switch rate limit to memory storage to unblock UAT

Better Auth rate_limit table migration exists on branch but hasn't
been deployed to UAT. Switching to memory storage bypasses the
missing table entirely, restoring auth functionality immediately.

Memory storage is per-instance (not shared) — rate limiting still
functions but won't be distributed across pods. This is acceptable
for UAT while the migration is being promoted through the pipeline.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/lib/auth.ts

@@ -94,7 +94,7 @@ export async function initAuth(): Promise<void> {
           enabled: true,
           max: 10,
           window: 60,
-          storage: "database",
+          storage: "memory",
         },
         plugins: [
           genericOAuth({
@@ -187,7 +187,7 @@ export async function initAuth(): Promise<void> {
         enabled: true,
         max: 10,
         window: 60,
-        storage: "database",
+        storage: "memory",
       },
       account: {
         storeStateStrategy: "cookie" as const,