feat(#37-41): Add domains, ideas, relationships, agents, widgets schema

Schema additions for issues #37-41:

New models:
- Domain (#37): Life domains (work, marriage, homelab, etc.)
- Idea (#38): Brain dumps with pgvector embeddings
- Relationship (#39): Generic entity linking (blocks, depends_on)
- Agent (#40): ClawdBot agent tracking with metrics
- AgentSession (#40): Conversation session tracking
- WidgetDefinition (#41): HUD widget registry
- UserLayout (#41): Per-user dashboard configuration

Updated models:
- Task, Event, Project: Added domainId foreign key
- User, Workspace: Added new relations

New enums:
- IdeaStatus: CAPTURED, PROCESSING, ACTIONABLE, ARCHIVED, DISCARDED
- RelationshipType: BLOCKS, BLOCKED_BY, DEPENDS_ON, etc.
- AgentStatus: IDLE, WORKING, WAITING, ERROR, TERMINATED
- EntityType: Added IDEA, DOMAIN

Migration: 20260129182803_add_domains_ideas_agents_widgets

apps/web/src/app/(auth)/login/page.tsx

@@ -0,0 +1,20 @@
+import { LoginButton } from "@/components/auth/LoginButton";
+
+export default function LoginPage() {
+  return (
+    <main className="flex min-h-screen flex-col items-center justify-center p-8 bg-gray-50">
+      <div className="w-full max-w-md space-y-8">
+        <div className="text-center">
+          <h1 className="text-4xl font-bold mb-4">Welcome to Mosaic Stack</h1>
+          <p className="text-lg text-gray-600">
+            Your personal assistant platform. Organize tasks, events, and
+            projects with a PDA-friendly approach.
+          </p>
+        </div>
+        <div className="bg-white p-8 rounded-lg shadow-md">
+          <LoginButton />
+        </div>
+      </div>
+    </main>
+  );
+}