feat: collapse Today sections

frontend/src/today-sections.css

@@ -0,0 +1,2 @@
+
+.today-section-toggle{width:100%;min-height:44px;display:flex;align-items:center;gap:10px;padding:8px 4px;border:0;background:transparent;color:var(--text-primary);text-align:left;border-radius:10px}.today-section-toggle:hover{background:var(--surface-raised)}.today-section-toggle:focus-visible{outline:2px solid var(--accent);outline-offset:2px}.today-section-title{display:flex;align-items:center;gap:8px;font-weight:800;font-size:15px}.today-section-title svg{width:17px;height:17px;color:var(--accent)}.today-section-summary{margin-left:auto;color:var(--muted);font-size:13px;font-weight:650}.today-section-toggle>svg{flex:0 0 auto;color:var(--muted)}.today-collapsible-section,.today-habits-section{min-width:0}.today-habits-section.today-section-anchor{scroll-margin-top:18px}