feat(dashboard): redesign UI with smart polling, unified sync card, filter bar

Replace SSE with smart polling (30s idle / 3s when running). Unify sync
panel into single two-row card with live progress text. Add unified filter
bar (period dropdown, status pills, search) with period-total counts.
Add Client/Cont tooltip for different shipping/billing persons. Add SKU
mappings pct_total badges + complete/incomplete filter + 409 duplicate
check. Add missing SKUs search + rescan progress UX. Migrate SQLite
orders schema (shipping_name, billing_name, payment_method,
delivery_method). Fix JSON_OUTPUT_DIR path for server running from
project root. Fix pagination controls showing top+bottom with per-page
selector (25/50/100/250).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/app/templates/mappings.html

@@ -3,6 +3,11 @@
 {% block nav_mappings %}active{% endblock %}
 
 {% block content %}
+<style>
+.badge-pct { font-size: 0.7rem; padding: 0.1rem 0.35rem; border-radius: 4px; font-weight: 600; }
+.badge-pct.complete { background: #d1fae5; color: #065f46; }
+.badge-pct.incomplete { background: #fef3c7; color: #92400e; }
+</style>
 <div class="d-flex justify-content-between align-items-center mb-4">
     <h4 class="mb-0">Mapari SKU</h4>
     <div>
@@ -36,6 +41,13 @@
     </div>
 </div>
 
+<!-- Percentage filter pills -->
+<div class="filter-bar" id="mappingsFilterBar">
+    <button class="filter-pill active" data-pct="all">Toate <span class="filter-count" id="mCntAll">0</span></button>
+    <button class="filter-pill" data-pct="complete">Complete &#10003; <span class="filter-count" id="mCntComplete">0</span></button>
+    <button class="filter-pill" data-pct="incomplete">Incomplete &#9888; <span class="filter-count" id="mCntIncomplete">0</span></button>
+</div>
+
 <!-- Table -->
 <div class="card">
     <div class="card-body p-0">