feat: allow configuring attachment upload limit (#12835)

## Summary
- add a configurable MAXIMUM_FILE_UPLOAD_SIZE installation setting and
surface it through super admin and global config payloads
- apply the configurable limit to attachment validations and shared
upload helpers on dashboard and widget
- introduce a reusable helper with unit tests for parsing the limit and
extend attachment specs for configurability


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[Codex
Task](https://chatgpt.com/codex/tasks/task_e_6912644786b08326bc8dee9401af6d0a)

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Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>

app/javascript/dashboard/mixins/fileUploadMixin.js

@@ -3,27 +3,48 @@ import { useAlert } from 'dashboard/composables';
 import { checkFileSizeLimit } from 'shared/helpers/FileHelper';
 import { getMaxUploadSizeByChannel } from '@chatwoot/utils';
 import { DirectUpload } from 'activestorage';
-import { MAXIMUM_FILE_UPLOAD_SIZE } from 'shared/constants/messages';
+import {
+  DEFAULT_MAXIMUM_FILE_UPLOAD_SIZE,
+  resolveMaximumFileUploadSize,
+} from 'shared/helpers/FileHelper';
+import { INBOX_TYPES } from 'dashboard/helper/inbox';
 
 export default {
   computed: {
     ...mapGetters({
       accountId: 'getCurrentAccountId',
     }),
+    installationLimit() {
+      return resolveMaximumFileUploadSize(
+        this.globalConfig.maximumFileUploadSize
+      );
+    },
   },
 
   methods: {
     maxSizeFor(mime) {
-      // Use default file size limit for private notes
+      // Use default/installation limit for private notes
       if (this.isOnPrivateNote) {
-        return MAXIMUM_FILE_UPLOAD_SIZE;
+        return this.installationLimit;
       }
 
-      return getMaxUploadSizeByChannel({
-        channelType: this.inbox?.channel_type,
+      const channelType = this.inbox?.channel_type;
+
+      if (!channelType || channelType === INBOX_TYPES.WEB) {
+        return this.installationLimit;
+      }
+
+      const channelLimit = getMaxUploadSizeByChannel({
+        channelType,
         medium: this.inbox?.medium, // e.g. 'sms' | 'whatsapp'
         mime, // e.g. 'image/png'
       });
+
+      if (channelLimit === DEFAULT_MAXIMUM_FILE_UPLOAD_SIZE) {
+        return this.installationLimit;
+      }
+
+      return Math.min(channelLimit, this.installationLimit);
     },
     alertOverLimit(maxSizeMB) {
       useAlert(

app/javascript/dashboard/mixins/specs/fileUploadMixin.spec.js

@@ -6,6 +6,8 @@ import { reactive } from 'vue';
 
 vi.mock('shared/helpers/FileHelper', () => ({
   checkFileSizeLimit: vi.fn(),
+  resolveMaximumFileUploadSize: vi.fn(value => Number(value) || 40),
+  DEFAULT_MAXIMUM_FILE_UPLOAD_SIZE: 40,
 }));
 
 vi.mock('activestorage', () => ({
@@ -27,6 +29,7 @@ describe('FileUploadMixin', () => {
   beforeEach(() => {
     mockGlobalConfig = reactive({
       directUploadsEnabled: true,
+      maximumFileUploadSize: 40,
     });
 
     mockCurrentChat = reactive({