fix: exponential backoff for 429 retries, cover thumbnails, 2 more modal dialogs

- matrix.ts: rateLimitedActions fallback delay now uses capped exponential
  backoff (min(1000 * 2^n, 30s)) instead of flat 3000ms when server omits
  Retry-After; server header still takes precedence
- RenderMessageContent: add objectFit:cover + 100% fill to video thumbnail
  <Image> so thumbnails fill their container without letterboxing (P5-6)
- CreateRoomModal, CreateSpaceModal: apply useModalStyle(480) for fullscreen
  on mobile
- LOTUS_BUGS: mark usePan memory leak + httpStatus check as FALSE POSITIVE;
  mark rateLimitedActions backoff as FIXED

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/components/RenderMessageContent.tsx

@@ -232,7 +232,13 @@ export function RenderMessageContent({
                       <ThumbnailContent
                         info={info}
                         renderImage={(src) => (
-                          <Image alt={body} title={body} src={src} loading="lazy" />
+                          <Image
+                            alt={body}
+                            title={body}
+                            src={src}
+                            loading="lazy"
+                            style={{ objectFit: 'cover', width: '100%', height: '100%' }}
+                          />
                         )}
                       />
                     )

src/app/features/create-room/CreateRoomModal.tsx

@@ -24,6 +24,7 @@ import {
 import { CreateRoomModalState } from '../../state/createRoomModal';
 import { stopPropagation } from '../../utils/keyboard';
 import { CreateRoomType } from '../../components/create-room/types';
+import { useModalStyle } from '../../hooks/useModalStyle';
 
 type CreateRoomModalProps = {
   state: CreateRoomModalState;
@@ -31,6 +32,7 @@ type CreateRoomModalProps = {
 function CreateRoomModal({ state }: CreateRoomModalProps) {
   const { spaceId, type } = state;
   const closeDialog = useCloseCreateRoomModal();
+  const modalStyle = useModalStyle(480);
 
   const allJoinedRooms = useAllJoinedRoomsSet();
   const getRoom = useGetRoom(allJoinedRooms);
@@ -48,7 +50,7 @@ function CreateRoomModal({ state }: CreateRoomModalProps) {
               escapeDeactivates: stopPropagation,
             }}
           >
-            <Modal size="300" flexHeight>
+            <Modal size="300" flexHeight style={modalStyle}>
               <Box direction="Column">
                 <Header
                   size="500"

src/app/features/create-space/CreateSpaceModal.tsx

@@ -23,6 +23,7 @@ import {
 } from '../../state/hooks/createSpaceModal';
 import { CreateSpaceModalState } from '../../state/createSpaceModal';
 import { stopPropagation } from '../../utils/keyboard';
+import { useModalStyle } from '../../hooks/useModalStyle';
 
 type CreateSpaceModalProps = {
   state: CreateSpaceModalState;
@@ -30,6 +31,7 @@ type CreateSpaceModalProps = {
 function CreateSpaceModal({ state }: CreateSpaceModalProps) {
   const { spaceId } = state;
   const closeDialog = useCloseCreateSpaceModal();
+  const modalStyle = useModalStyle(480);
 
   const allJoinedRooms = useAllJoinedRoomsSet();
   const getRoom = useGetRoom(allJoinedRooms);
@@ -47,7 +49,7 @@ function CreateSpaceModal({ state }: CreateSpaceModalProps) {
               escapeDeactivates: stopPropagation,
             }}
           >
-            <Modal size="300" flexHeight>
+            <Modal size="300" flexHeight style={modalStyle}>
               <Box direction="Column">
                 <Header
                   size="500"

src/app/utils/matrix.ts

@@ -364,7 +364,8 @@ export const rateLimitedActions = async <T, R = void>(
         return;
       }
 
-      const waitMS = err.getRetryAfterMs() ?? 3000;
+      // Respect server Retry-After header; fall back to capped exponential backoff.
+      const waitMS = err.getRetryAfterMs() ?? Math.min(1000 * 2 ** retryCount, 30_000);
       actionInterval = waitMS * 1.5;
       await sleepForMs(waitMS);
       retryCount += 1;