Adds a subtle, repeating SVG pattern behind the message thread and the
"select a conversation" empty state — same visual language WhatsApp uses
in their own chat UI, themed for a CRM (message bubble, phone, mail,
calendar, lightbulb, briefcase, trophy, dollar sign, percent, etc).
Asset: public/inbox-doodle.svg, 6 KB, 240×240 tile that repeats
seamlessly. Icon shapes are taken verbatim from lucide-react (already
a dependency, every other icon in the UI uses it) so the doodle reads
as part of the same visual system, not a separate clip-art import.
Stroke is slate-500 at 22% opacity over bg-slate-950 — visible but
not competing with message text.
Wiring: a single DOODLE_BG_CLASSES constant in message-thread.tsx
applied to both the empty-state and active-thread containers, so they
can't drift. The header keeps bg-slate-900 (solid) and the composer
keeps its own background, so the doodle only shows in the actual
message scroll area — exactly like WhatsApp.
No JS, no perf hit beyond a one-off 6 KB asset fetch that's then
browser-cached forever (it's served from /public with Next's default
caching).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
