feat: per-user assistant name and system prompt customization

Each user can rename the AI assistant and edit their own system prompt in Settings.

src/app/layout.tsx

@@ -18,6 +18,7 @@ import { InstallPrompt } from "@/components/install-prompt";
 import { AppShell } from "@/components/app-shell";
 import { AppToaster } from "@/components/app-toaster";
 import { AssistantBubble } from "@/modules/agent/components/assistant-bubble";
+import { DEFAULT_ASSISTANT_NAME } from "@/lib/assistant-config";
 import { isLlmConfigured } from "@/lib/llm";
 import { DEFAULT_THEME, navStyleToDataNav } from "@/modules/_core/themes";
 import type { Palette, ThemeMode, FontPair, Density, NavStyle } from "@/modules/_core/themes";
@@ -102,6 +103,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
   let userDashboards: DashboardMeta[] = [];
   let signedIn = false;
   let assistantEnabled = false;
+  let assistantName = DEFAULT_ASSISTANT_NAME;
 
   const session = await auth();
   if (session?.user?.id) {
@@ -114,6 +116,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
         themeDensity: users.themeDensity,
         themeNavStyle: users.themeNavStyle,
         assistantEnabled: users.assistantEnabled,
+        assistantName: users.assistantName,
       })
       .from(users)
       .where(eq(users.id, session.user.id))
@@ -125,6 +128,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
       density = row.themeDensity as Density;
       navStyle = row.themeNavStyle as NavStyle;
       assistantEnabled = row.assistantEnabled;
+      assistantName = row.assistantName?.trim() || DEFAULT_ASSISTANT_NAME;
     }
     userDashboards = await db
       .select({
@@ -178,7 +182,11 @@ export default async function RootLayout({ children }: { children: React.ReactNo
           <InstallPrompt />
           <PwaRegister />
           {signedIn && assistantEnabled && session?.user?.id ? (
-            <AssistantBubble configured={isLlmConfigured()} userId={session.user.id} />
+            <AssistantBubble
+              configured={isLlmConfigured()}
+              userId={session.user.id}
+              assistantName={assistantName}
+            />
           ) : null}
           <AppToaster position="bottom-right" />
         </QuickAddProvider>