docs(flutter): document multi-attachment upload, composer & bubbles

[anshuman-cometchat]

Add Flutter multimedia/multi-attachment documentation, mirroring the structure of the Android multimedia docs.

• sdk/flutter: split the UploadFileRequest upload API into a dedicated upload-files page; send-message now links to it.
• ui-kit/flutter/message-composer: Multiple Attachments section (Limits and Validation / Disabling / Styling the Attachment Tray).
• ui-kit/flutter/message-list: Multiple Attachments grouping.
• ui-kit/flutter/message-bubble-styling: Images / Videos / Audios / Files bubbles with reference screenshots.
• docs.json: add sdk/flutter/upload-files to the navigation.

Description

Related Issue(s)

Type of Change

• Documentation correction/update
• New documentation
• Improvement to existing documentation
• Typo fix
• Other (please specify)

Checklist

• I have read the CONTRIBUTING document
• My branch name follows the naming convention
• My changes follow the documentation style guide
• I have checked for spelling and grammar errors
• All links in my changes are valid and working
• My changes are accurately described in this pull request

Additional Information

Screenshots (if applicable)

[jitvarpatil]

Docs review — ✅ Approve

Flutter multi-attachment docs — the 4th and final platform in this series (after iOS #428, Android #430, RN #432), with a new 253-line upload-files.mdx. Every symbol verified against the Flutter SDK, and notably this one is verified against master-v5 (already released, v5.0.6) rather than an unmerged feature branch.

✅ API — verified against Flutter SDK master-v5 (v5.0.6)

• CometChat.createUploadFileRequest + uploadAttachments + UploadFileListener + UploadResult — lib/handlers/upload_file_listener.dart
• UploadFileRequest — lib/src/domain/models/upload/upload_file_request.dart
• UploadFileListener callbacks match exactly: onFileProgress(String fileId, int loaded, int total, int percent), onFileUploaded(String, Attachment), onFileError, onFileFailure, onComplete(UploadResult)
• getMaxAttachmentCount(): int and getMaxAttachmentSize(): int

Platform precision 👏 — Flutter is the third distinct naming variant in this series and the docs get it right: getMaxAttachmentSize (Flutter) vs getMaxFileSize (iOS/Android) vs RN's async getMaxAttachmentCount with no size getter. getMaxFileSize is correctly absent here. Across all four platform PRs, nobody copy-pasted another platform's API names.

✅ Structure

New sdk/flutter/upload-files wired into nav; 0 nav breaks, 0 orphans, 0 broken links. All 4 bubble images are under the standard images/ directory (unlike #428, where I flagged a non-standard path) and are referenced by message-bubble-styling.mdx.

🟡 P2 — notes (non-blocking)

• The 4 bubble images (audiobubble/filesbubble/imagesbubble/videosbubble.png) are byte-identical to the ones docs(android): enhance multimedia attachment #430 (Android) adds. Identical content = no merge conflict, but please confirm they actually depict Flutter's rendering rather than Android's being reused; if they differ visually in practice, use per-platform files.
• imagesbubble.png (841 KB) and videosbubble.png (672 KB) are hefty (~1.5 MB for two) — worth compressing.

Well-sourced, platform-precise PR. Ready to merge. 🚀

_{🤖 Automated docs review (Mintlify link/redirect/content checks + API verification against cometchat_sdk Flutter master-v5 / v5.0.6).}

[jitvarpatil]

Docs review — ✅ Approve

Flutter multi-attachment docs — the 4th and final platform in this series (after iOS #428, Android #430, RN #432), with a new 253-line upload-files.mdx. Every symbol verified against the Flutter SDK, and notably this one is verified against master-v5 (already released, v5.0.6) rather than an unmerged feature branch.

✅ API — verified against Flutter SDK master-v5 (v5.0.6)

• CometChat.createUploadFileRequest + uploadAttachments + UploadFileListener + UploadResult — lib/handlers/upload_file_listener.dart
• UploadFileRequest — lib/src/domain/models/upload/upload_file_request.dart
• UploadFileListener callbacks match exactly: onFileProgress(String fileId, int loaded, int total, int percent), onFileUploaded(String, Attachment), onFileError, onFileFailure, onComplete(UploadResult)
• getMaxAttachmentCount(): int and getMaxAttachmentSize(): int

Platform precision 👏 — Flutter is the third distinct naming variant in this series and the docs get it right: getMaxAttachmentSize (Flutter) vs getMaxFileSize (iOS/Android) vs RN's async getMaxAttachmentCount with no size getter. getMaxFileSize is correctly absent here. Across all four platform PRs, nobody copy-pasted another platform's API names.

✅ Structure

New sdk/flutter/upload-files wired into nav; 0 nav breaks, 0 orphans, 0 broken links. All 4 bubble images are under the standard images/ directory (unlike #428, where I flagged a non-standard path) and are referenced by message-bubble-styling.mdx.

🟡 P2 — notes (non-blocking)

• The 4 bubble images (audiobubble/filesbubble/imagesbubble/videosbubble.png) are byte-identical to the ones #430 (Android) adds. Identical content = no merge conflict, but please confirm they actually depict Flutter's rendering rather than Android's being reused; if they differ visually in practice, use per-platform files.
• imagesbubble.png (841 KB) and videosbubble.png (672 KB) are hefty (~1.5 MB for two) — worth compressing.

Well-sourced, platform-precise PR. Ready to merge. 🚀

_{🤖 Automated docs review (Mintlify link/redirect/content checks + API verification against cometchat_sdk Flutter master-v5 / v5.0.6).}