polish(v0.7): replace timeline 📜 + push 🔔 emoji with themed line icons

Swap the two v0.7 emoji buttons for lucide line icons (stroke=currentColor) so
they take the Amber theme colour like the toolbar icons:
- timeline toggle (tabs.ts) → scroll-text icon
- push toggle + disabled bell (push.ts) → bell icon, keeping the On/Off label
- icons.ts: ICON_TIMELINE, ICON_BELL; style.css sizes the inline svgs (16px)

Frontend-only. web tsc + build:web clean, 102 push tests green, bundle emoji-free.

public/icons.ts

@@ -43,3 +43,6 @@ export const ICON_HISTORY = lineIcon('<path d="M3 12a9 9 0 1 0 9-9 9.75 9.75 0 0
 export const ICON_KEYBOARD = lineIcon('<path d="M10 8h.01" /> <path d="M12 12h.01" /> <path d="M14 8h.01" /> <path d="M16 12h.01" /> <path d="M18 8h.01" /> <path d="M6 8h.01" /> <path d="M7 16h10" /> <path d="M8 12h.01" /> <rect width="20" height="16" x="2" y="4" rx="2" />')
 export const ICON_SHARE = lineIcon('<circle cx="18" cy="5" r="3" /> <circle cx="6" cy="12" r="3" /> <circle cx="18" cy="19" r="3" /> <line x1="8.59" x2="15.42" y1="13.51" y2="17.49" /> <line x1="15.41" x2="8.59" y1="6.51" y2="10.49" />')
 export const ICON_DEVICE = lineIcon('<rect width="14" height="20" x="5" y="2" rx="2" ry="2" /> <path d="M12 18h.01" />')
+
+export const ICON_BELL = lineIcon('<path d="M10.268 21a2 2 0 0 0 3.464 0" /> <path d="M3.262 15.326A1 1 0 0 0 4 17h16a1 1 0 0 0 .74-1.673C19.41 13.956 18 12.499 18 8A6 6 0 0 0 6 8c0 4.499-1.411 5.956-2.738 7.326" />')
+export const ICON_TIMELINE = lineIcon('<path d="M15 12h-5" /> <path d="M15 8h-5" /> <path d="M19 17V5a2 2 0 0 0-2-2H4" /> <path d="M8 21h12a2 2 0 0 0 2-2v-1a1 1 0 0 0-1-1H11a1 1 0 0 0-1 1v1a2 2 0 1 1-4 0V5a2 2 0 1 0-4 0v2a1 1 0 0 0 1 1h3" />')