feat: Implement remote user profile caching and enhance chat conversation list display with updated styling.

src/lib/swarm/user-cache.ts

@@ -0,0 +1,49 @@
+import { db, users } from '@/db';
+import { eq } from 'drizzle-orm';
+
+export interface RemoteProfile {
+    handle: string;
+    displayName: string;
+    avatarUrl?: string | null;
+    did: string;
+    isBot?: boolean;
+}
+
+/**
+ * Upsert a remote user into the local database for caching/display purposes.
+ */
+export async function upsertRemoteUser(profile: RemoteProfile) {
+    try {
+        if (!db) return;
+
+        // Check if user already exists
+        const existing = await db.query.users.findFirst({
+            where: eq(users.did, profile.did),
+        });
+
+        if (existing) {
+            // Update metadata if changed
+            await db.update(users)
+                .set({
+                    displayName: profile.displayName || existing.displayName,
+                    avatarUrl: profile.avatarUrl || existing.avatarUrl,
+                    isBot: profile.isBot ?? existing.isBot,
+                    updatedAt: new Date(),
+                })
+                .where(eq(users.id, existing.id));
+        } else {
+            // Create new placeholder user
+            await db.insert(users).values({
+                did: profile.did,
+                handle: profile.handle, // user@domain
+                displayName: profile.displayName || profile.handle,
+                avatarUrl: profile.avatarUrl || null,
+                isBot: profile.isBot || false,
+                publicKey: '', // We don't necessarily have their public key yet, but DMs often do
+                // Note: nodeId is null for remote placeholders unless we specifically link it
+            });
+        }
+    } catch (error) {
+        console.error(`[User Cache] Failed to upsert ${profile.handle}:`, error);
+    }
+}