feat: forum rich-text editor, emoji picker, mentions, discover nav, feed, uploads, profile

Forum:
- TipTap WYSIWYG editor with full toolbar
- @emoji-mart/react emoji picker (consistent with tweets)
- @mention autocomplete with user search API
- Fix PHP 8.4 parse errors in Blade templates
- Fix thread data display (paginator items)
- Align forum page widths to max-w-5xl

Discover:
- Extract shared _nav.blade.php partial
- Add missing nav links to for-you page
- Add Following link for authenticated users

Feed/Posts:
- Post model, controllers, policies, migrations
- Feed page components (PostComposer, FeedCard, etc)
- Post reactions, comments, saves, reports, sharing
- Scheduled publishing support
- Link preview controller

Profile:
- Profile page components (ProfileHero, ProfileTabs)
- Profile API controller

Uploads:
- Upload wizard enhancements
- Scheduled publish picker
- Studio status bar and readiness checklist

app/Http/Controllers/Studio/StudioArtworksApiController.php

@@ -13,6 +13,7 @@ use App\Services\Studio\StudioBulkActionService;
 use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Log;
+use Illuminate\Support\Facades\File;
 use Illuminate\Support\Facades\Validator;
 use Symfony\Component\HttpKernel\Exception\TooManyRequestsHttpException;
 
@@ -318,15 +319,17 @@ final class StudioArtworksApiController extends Controller
             $storage      = app(\App\Services\Uploads\UploadStorageService::class);
             $artworkFiles = app(\App\Repositories\Uploads\ArtworkFileRepository::class);
 
-            // 1. Store original on disk
+            // 1. Store original on disk (preserve extension when possible)
             $originalPath     = $derivatives->storeOriginal($tempPath, $hash);
-            $originalRelative = $storage->sectionRelativePath('originals', $hash, 'orig.webp');
-            $artworkFiles->upsert($artwork->id, 'orig', $originalRelative, 'image/webp', (int) filesize($originalPath));
+            $origFilename     = basename($originalPath);
+            $originalRelative = $storage->sectionRelativePath('original', $hash, $origFilename);
+            $origMime         = File::exists($originalPath) ? File::mimeType($originalPath) : 'application/octet-stream';
+            $artworkFiles->upsert($artwork->id, 'orig', $originalRelative, $origMime, (int) filesize($originalPath));
 
-            // 2. Generate public derivatives (thumbnails)
+            // 2. Generate thumbnails (xs/sm/md/lg/xl)
             $publicAbsolute = $derivatives->generatePublicDerivatives($tempPath, $hash);
             foreach ($publicAbsolute as $variant => $absolutePath) {
-                $relativePath = $storage->publicRelativePath($hash, $variant . '.webp');
+                $relativePath = $storage->sectionRelativePath($variant, $hash, $hash . '.webp');
                 $artworkFiles->upsert($artwork->id, $variant, $relativePath, 'image/webp', (int) filesize($absolutePath));
             }
 
@@ -337,13 +340,14 @@ final class StudioArtworksApiController extends Controller
             $size   = (int) filesize($originalPath);
 
             // 4. Update the artwork's file-serving fields (hash drives thumbnail URLs)
+            $origExt = strtolower(pathinfo($originalPath, PATHINFO_EXTENSION) ?: '');
             $artwork->update([
-                'file_name' => 'orig.webp',
+                'file_name' => $origFilename,
                 'file_path' => '',
                 'file_size' => $size,
-                'mime_type' => 'image/webp',
+                'mime_type' => $origMime,
                 'hash'      => $hash,
-                'file_ext'  => 'webp',
+                'file_ext'  => $origExt,
                 'thumb_ext' => 'webp',
                 'width'     => max(1, $width),
                 'height'    => max(1, $height),