Parameterize image max dimension and blob size

Replace the hardcoded POST_IMG_MAX limits baked into the resize helpers
with explicit per-caller maxDimension/maxBytes parameters. Pasted image
URLs now pre-shrink at the high-res 4000px/2MB post limits instead of
2000px/1MB, removing a quality bottleneck before compressImage runs.
Avatar/banner/onboarding and link thumbnails keep their 2000px/1MB
limits.

Also bring web doResize to parity with native by clamping dimensions via
a shared getResizedDimensions (hoisted into media/util.ts), and shadow
the mutated maxDimension param in compressImage as a local.

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

src/view/com/composer/text-input/TextInput.tsx

@@ -16,7 +16,7 @@ import {type PasteEventPayload, TextInputWrapper} from 'expo-paste-input'
 import {AppBskyRichtextFacet, RichText} from '@atproto/api'
 import {useLingui} from '@lingui/react/macro'
 
-import {POST_IMG_MAX} from '#/lib/constants'
+import {POST_IMG_MAX_HIGH_RES} from '#/lib/constants'
 import {downloadAndResize} from '#/lib/media/manip'
 import {isUriImage} from '#/lib/media/util'
 import {getMentionAt, insertMentionAt} from '#/lib/strings/mention-manip'
@@ -93,10 +93,8 @@ export function TextInput({
               if (isUriImage(feature.uri)) {
                 const res = await downloadAndResize({
                   uri: feature.uri,
-                  width: POST_IMG_MAX.width,
-                  height: POST_IMG_MAX.height,
-                  mode: 'contain',
-                  maxSize: POST_IMG_MAX.size,
+                  maxDimension: POST_IMG_MAX_HIGH_RES.width,
+                  maxSize: POST_IMG_MAX_HIGH_RES.size,
                   timeout: 15e3,
                 })