feat: configurable upload file size limits via .env (#695)

* feat: make upload file size limits configurable via .env

Add UPLOAD_MAX_*_MB environment variables for documents, images, videos,
exercise assignment files, AI assistant documents, landing page images,
and media thumbnails. API presign routes validate file size server-side;
dashboard UI reads the same limits from layout data.

* chore: wire upload limit env vars through Docker compose and docs

Pass UPLOAD_MAX_*_MB from the root .env into api and dashboard containers
in both compose files, document them in .env.example and self-hosting guides.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* docs: cross-link upload limits in README, Railway, Coolify, and Cloudflare guides

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix: address PR review feedback on upload limits

- Restore 5 MB default for thumbnail uploads (edit-asset-dialog regression)
- Add getResolvedUploadLimits() fallback for Storybook/tests
- Cache core getUploadLimits() like the dashboard helper
- Document presign fileSize as advisory; allow zero-byte fileSize in schema
- Only send fileSize to presign when greater than zero

* docs: remove upload limits from Cloudflare setup guide

---------

apps/dashboard/src/lib/features/course/components/lesson/document/add-document-modal.svelte

@@ -14,6 +14,7 @@
   import * as Dialog from '@cio/ui/base/dialog';
   import * as FileDropZone from '@cio/ui/custom/file-drop-zone';
   import type { FileRejectedReason } from '@cio/ui/custom/file-drop-zone';
+  import { getResolvedUploadLimits } from '$lib/utils/config/upload-limits-context';
 
   interface Props {
     lessonId?: string;
@@ -34,7 +35,8 @@
     'application/msword'
   ];
 
-  const MAX_DOCUMENT_SIZE = 5 * 1024 * 1024; // 5MB
+  const uploadLimits = getResolvedUploadLimits();
+  const maxDocumentSize = uploadLimits.documentBytes;
 
   const documentUploader = new DocumentUploader();
 
@@ -58,9 +60,9 @@
       return $t('course.navItem.lessons.materials.tabs.document.file_type_error');
     }
 
-    if (file.size > MAX_DOCUMENT_SIZE) {
+    if (file.size > maxDocumentSize) {
       return $t('course.navItem.lessons.materials.tabs.document.file_size_error', {
-        size: formatFileSize(MAX_DOCUMENT_SIZE)
+        size: formatFileSize(maxDocumentSize)
       });
     }
 
@@ -87,7 +89,7 @@
     if (opts.reason === 'Maximum file size exceeded') {
       snackbar.error(
         $t('course.navItem.lessons.materials.tabs.document.file_size_error', {
-          size: formatFileSize(MAX_DOCUMENT_SIZE)
+          size: formatFileSize(maxDocumentSize)
         })
       );
     } else if (opts.reason === 'File type not allowed') {
@@ -259,7 +261,7 @@
             accept=".pdf,.docx,.doc,application/pdf,application/vnd.openxmlformats-officedocument.wordprocessingml.document,application/msword"
             maxFiles={1}
             fileCount={0}
-            maxFileSize={MAX_DOCUMENT_SIZE}
+            maxFileSize={maxDocumentSize}
             onUpload={handleFilesUpload}
             onFileRejected={handleFileRejected}
           >

apps/dashboard/src/lib/features/course/components/lesson/video/upload-video.svelte

@@ -14,6 +14,7 @@
   import { mediaApi } from '$features/media/api';
   import { JobPoller, jobsApi, type MediaJobEnvelope } from '$features/jobs';
   import { onDestroy } from 'svelte';
+  import { getResolvedUploadLimits } from '$lib/utils/config/upload-limits-context';
 
   const ADD_VIDEO = 'course.navItem.lessons.materials.tabs.video.add_video';
   const PROCESSING_BASE = `${ADD_VIDEO}.processing`;
@@ -50,6 +51,9 @@
 
   const isDisabled = $derived($lessonVideoUpload.isUploading || $isFreePlan);
 
+  const uploadLimits = getResolvedUploadLimits();
+  const maxVideoSize = uploadLimits.videoBytes;
+
   const videoUploader = new VideoUploader();
   const mediaUploader = new MediaUploader();
 
@@ -401,7 +405,7 @@
         accept="video/*"
         maxFiles={1}
         fileCount={0}
-        maxFileSize={800 * FileDropZone.MEGABYTE}
+        maxFileSize={maxVideoSize}
         onUpload={handleUpload}
         {onFileRejected}
       >