Chat fills the space next to the sidebar (no more dead strip)

The conversation column was max-w-3xl and centred, which on a 1280 window
left a ~140px empty strip between the rail and the messages - "the chat
cuts off weirdly". It now uses the library's container (max-w-6xl,
lg:px-10) and the composer's content padding matches, so the chat starts
right next to the sidebar and every row shares one left edge.

Contrast 0 findings, chat 102/102, mobile 126/126, i18n 13/13,
native 33/33. Version 0.5.0 (the 0.4.9 rollover), SW -> freezmo-v74.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "freezmo",
-  "version": "0.4.9",
+  "version": "0.5.0",
   "private": true,
   "license": "GPL-3.0-only",
   "scripts": {