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/components/layout/Navigation.tsx

@@ -0,0 +1,56 @@
+"use client";
+
+import { usePathname } from "next/navigation";
+import Link from "next/link";
+import { useAuth } from "@/lib/auth/auth-context";
+import { LogoutButton } from "@/components/auth/LogoutButton";
+
+export function Navigation() {
+  const pathname = usePathname();
+  const { user } = useAuth();
+
+  const navItems = [
+    { href: "/tasks", label: "Tasks" },
+    { href: "/calendar", label: "Calendar" },
+  ];
+
+  return (
+    <nav className="fixed top-0 left-0 right-0 bg-white border-b border-gray-200 z-50">
+      <div className="container mx-auto px-4">
+        <div className="flex items-center justify-between h-16">
+          <div className="flex items-center gap-8">
+            <Link href="/tasks" className="text-xl font-bold text-gray-900">
+              Mosaic Stack
+            </Link>
+            <div className="flex gap-4">
+              {navItems.map((item) => {
+                const isActive = pathname === item.href;
+                return (
+                  <Link
+                    key={item.href}
+                    href={item.href}
+                    className={`px-3 py-2 rounded-md text-sm font-medium transition-colors ${
+                      isActive
+                        ? "bg-blue-100 text-blue-700"
+                        : "text-gray-600 hover:bg-gray-100"
+                    }`}
+                  >
+                    {item.label}
+                  </Link>
+                );
+              })}
+            </div>
+          </div>
+          <div className="flex items-center gap-4">
+            {user && (
+              <div className="text-sm text-gray-600">
+                {user.name || user.email}
+              </div>
+            )}
+            <LogoutButton variant="secondary" />
+          </div>
+        </div>
+      </div>
+    </nav>
+  );
+}