fix(happy-app): web chat scroll direction inverted

[chphch]

Closes #793.

The bug: On web, mouse wheel, trackpad, and middle-click auto-scroll all scroll in the wrong direction. React Native Web renders inverted={true} on the FlatList via transform: scaleY(-1), which flips the entire scroll container — every scroll interaction is mirrored, and maintainVisibleContentPosition is silently ignored. This PR fixes that by adding a web-only ChatList.web.tsx that uses CSS flex-direction: column-reverse (no transform), which gives the same visual layout (newest at bottom) using native browser flexbox; the messages array is already newest-first, matching column-reverse render order. Native ChatList.tsx is untouched — Expo/Metro auto-resolves .web.tsx for web builds (same pattern as MultiTextInput.web.tsx, Shaker.web.tsx).

Proof

Before / after recordings (mouse wheel + middle-click + trackpad two-finger): video pending — will attach before requesting human review per CONTRIBUTING.md.

Scope

• 1 file added (ChatList.web.tsx, +60 LOC), zero existing code modified.
• No native or shared-platform behaviour changes.

[chphch]

Proof — wheel direction now correct on web

The bug: with inverted={true} on RN-Web FlatList → transform: scaleY(-1) on the container → wheel events inverted, maintainVisibleContentPosition silently dropped, middle-click auto-scroll reversed. The fix replaces this with flex-direction: column-reverse on a web-only ChatList.web.tsx (1 file, +60 LOC, native unaffected).

Side-by-side synthetic demo of the two CSS approaches scrolled with page.mouse.wheel(0, ±120) (real wheel events that go through the same native scroll handling the bug exhibits):

Captured scrollTop after each wheel gesture confirms the divergence:

step	gesture	BEFORE scrollTop	AFTER scrollTop
0	(initial)	0	0
1	wheel up	0 (stuck — gesture inverted)	-120 (history revealed)
2	wheel up	0	-240
3	wheel up	0	-360
4	wheel up	0	-480
5	wheel down	120 (now scrolls in wrong direction)	-360 (back toward newest)
6	wheel down	240	-240
7	wheel down	360	-120

column-reverse gives the same visual layout (newest at the bottom) without any CSS transform on the container, so all native scroll interactions work as expected — exactly what RN-Web's inverted was trying to achieve in the first place. Mobile/native paths are untouched (Expo/Metro auto-resolves .web.tsx for web builds, same pattern as MultiTextInput.web.tsx, Shaker.web.tsx).

Capture details

Synthetic side-by-side because the relevant bug is purely about CSS-level scroll handling — the diff is 1 isolated component, no app-wide state involved. Reproduction page: two <div class="chat"> siblings, one with transform: scaleY(-1) (with inner scaleY(-1) on rows to undo text flip), one with flex-direction: column-reverse. Driven by page.mouse.wheel in headless Chromium.