Add user authentication with login/register

- Add users and sessions tables to database schema
- Add bcryptjs for password hashing
- Create auth API routes (login, register, logout, me)
- Add AuthProvider context for client-side auth state
- Update all API routes to require authentication and filter by userId
- Create login and register pages
- Add AppShell component for authenticated layout
- Update all pages to use AppShell and show user info
- Each user now has their own private entries and tags

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/timeline/page.tsx

@@ -1,6 +1,7 @@
 "use client";
 
-import { useState, useEffect, useCallback } from "react";
+import { useState, useEffect } from "react";
+import { AppShell } from "@/components/AppShell";
 import { WeeklyReflection } from "@/components/WeeklyReflection";
 import { FilterPanel } from "@/components/FilterPanel";
 import { EntryRow } from "@/components/EntryRow";
@@ -56,7 +57,7 @@ export default function TimelinePage() {
   }, [entries, filters]);
 
   return (
-    <div>
+    <AppShell>
       <header className="mb-6">
         <h1 className="text-2xl font-light">{APP_NAME}</h1>
         <p className="text-sm text-muted">Timeline</p>
@@ -88,6 +89,6 @@ export default function TimelinePage() {
           )}
         </>
       )}
-    </div>
+    </AppShell>
   );
 }