Accounts Phase 4: prefs sync + account/settings panel

- Prefs sync: GET/PUT /api/prefs store Calm Filters/Boundaries on the account.
  On sign-in the client adopts the account's prefs if present, else seeds them
  from the device; every change PUTs to the account so tuning follows you across
  devices. (Login side-effects run under untrack so browsing doesn't re-trigger.)
- Account panel: GET /api/account (email, connected sign-in methods, saved count,
  active sessions); Export my data (GET /api/account/export → JSON download);
  Sign out everywhere (revoke all sessions); Delete account (cascades to all
  account data) with an inline confirm. Reachable from You → Account.

Deferred to a follow-up: link/unlink a provider (OAuth link-mode) and per-session
revoke. 118 tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/AccountPanel.svelte

@@ -0,0 +1,119 @@
+<script>
+  import { onMount } from 'svelte';
+  import { getJSON, postJSON, delJSON } from '$lib/api.js';
+  import { clearLocal } from '$lib/auth.svelte.js';
+
+  let { onclose } = $props();
+  let info = $state(null);
+  let error = $state('');
+  let confirmingDelete = $state(false);
+  let busy = $state('');
+
+  const PROVIDER_LABEL = { email: 'Email link', google: 'Google', apple: 'Apple' };
+
+  onMount(async () => {
+    try {
+      info = await getJSON('/api/account');
+    } catch {
+      error = "Couldn't load your account.";
+    }
+  });
+
+  async function logoutEverywhere() {
+    busy = 'logout';
+    try {
+      await postJSON('/api/account/logout-all', {});
+      clearLocal();
+      onclose?.();
+    } catch {
+      error = 'Could not sign out everywhere — try again.';
+    } finally {
+      busy = '';
+    }
+  }
+
+  async function deleteAccount() {
+    busy = 'delete';
+    try {
+      await delJSON('/api/account');
+      clearLocal();
+      onclose?.();
+    } catch {
+      error = 'Could not delete the account — try again.';
+    } finally {
+      busy = '';
+    }
+  }
+</script>
+
+<section class="panel rise">
+  <div class="phead">
+    <h2>Account</h2>
+    <button class="close" onclick={onclose}>done</button>
+  </div>
+
+  {#if error}<p class="err">{error}</p>{/if}
+
+  {#if info}
+    <div class="row"><span class="k">Email</span><span class="v">{info.user.email}</span></div>
+    <div class="row">
+      <span class="k">Sign-in methods</span>
+      <span class="v">{info.providers.map((p) => PROVIDER_LABEL[p] ?? p).join(', ')}</span>
+    </div>
+    <div class="row"><span class="k">Saved articles</span><span class="v">{info.saved_count}</span></div>
+    <div class="row"><span class="k">Active sessions</span><span class="v">{info.sessions}</span></div>
+
+    <div class="actions">
+      <a class="btn" href="/api/account/export">Export my data</a>
+      <button class="btn" onclick={logoutEverywhere} disabled={busy === 'logout'}>
+        {busy === 'logout' ? 'Signing out…' : 'Sign out everywhere'}
+      </button>
+    </div>
+
+    <div class="danger">
+      {#if !confirmingDelete}
+        <button class="link-danger" onclick={() => (confirmingDelete = true)}>Delete my account</button>
+      {:else}
+        <p class="warn">This permanently removes your account, saved articles, and history. This can't be undone.</p>
+        <div class="actions">
+          <button class="btn danger-btn" onclick={deleteAccount} disabled={busy === 'delete'}>
+            {busy === 'delete' ? 'Deleting…' : 'Yes, delete everything'}
+          </button>
+          <button class="btn" onclick={() => (confirmingDelete = false)}>Cancel</button>
+        </div>
+      {/if}
+    </div>
+
+    <p class="fine">Browsing without an account still works — signing out keeps your saved items safe on the server for next time.</p>
+  {:else if !error}
+    <p class="muted">Loading…</p>
+  {/if}
+</section>
+
+<style>
+  .row {
+    display: flex; justify-content: space-between; gap: 16px;
+    padding: 10px 2px; border-bottom: 1px solid var(--line); font-size: 0.92rem;
+  }
+  .row .k { color: var(--muted); }
+  .row .v { color: var(--ink); text-align: right; }
+  .actions { display: flex; flex-wrap: wrap; gap: 10px; margin: 16px 0 6px; }
+  .btn {
+    font: inherit; font-size: 0.86rem; font-weight: 600;
+    border: 1px solid var(--line); border-radius: 999px; padding: 8px 14px;
+    background: var(--surface); color: var(--accent-deep); cursor: pointer; text-decoration: none;
+  }
+  .btn:hover { background: var(--accent-soft); }
+  .btn:disabled { opacity: 0.6; cursor: default; }
+  .danger { margin-top: 18px; padding-top: 14px; border-top: 1px solid var(--line); }
+  .link-danger {
+    background: none; border: none; color: #9a3b3b; font-size: 0.86rem;
+    text-decoration: underline; cursor: pointer; padding: 0;
+  }
+  .warn { color: #9a3b3b; font-size: 0.88rem; margin: 0 0 10px; }
+  .danger-btn { color: #fff; background: #9a3b3b; border-color: #9a3b3b; }
+  .danger-btn:hover { background: #843232; }
+  .err { color: #9a3b3b; font-size: 0.86rem; }
+  .fine { margin-top: 16px; color: var(--muted); font-size: 0.8rem; }
+  .muted { color: var(--muted); }
+</style>