Rename image size constants and require them as params

POST_IMG_MAX no longer described post images, so rename it to the
semantically accurate pair: POST_IMG_MAX_SIZE (4000px/2MB, post images
and pasted URLs) and PROFILE_IMAGES_MAX_SIZE (2000px/1MB, avatars,
banners, onboarding, link thumbnails).

Drop the constant defaults from compressImage, compressIfNeeded, and
getResizedDimensions; callers now pass the appropriate max config object
directly so the size policy lives at the call site. Web avatar/banner
edits now use PROFILE_IMAGES_MAX_SIZE, matching the native profile path.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/view/com/util/UserAvatar.tsx

@@ -17,6 +17,7 @@ import {useLingui} from '@lingui/react'
 import {Trans} from '@lingui/react/macro'
 import {useQueryClient} from '@tanstack/react-query'
 
+import {PROFILE_IMAGES_MAX_SIZE} from '#/lib/constants'
 import {useHaptics} from '#/lib/haptics'
 import {
   useCameraPermission,
@@ -394,6 +395,7 @@ let EditableUserAvatar = ({
         await openCamera({
           aspect: [1, 1],
         }),
+        PROFILE_IMAGES_MAX_SIZE,
       ),
     )
   }, [onSelectNewAvatar, requestCameraAccessIfNeeded])
@@ -422,6 +424,7 @@ let EditableUserAvatar = ({
               shape: circular ? 'circle' : 'rectangle',
               aspectRatio: 1,
             }),
+            PROFILE_IMAGES_MAX_SIZE,
           ),
         )
       } else {
@@ -448,7 +451,7 @@ let EditableUserAvatar = ({
 
   const onChangeEditImage = useCallback(
     async (image: ComposerImage) => {
-      const compressed = await compressImage(image)
+      const compressed = await compressImage(image, PROFILE_IMAGES_MAX_SIZE)
       onSelectNewAvatar(compressed)
     },
     [onSelectNewAvatar],