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/Api/Posts/PostSaveController.php

@@ -0,0 +1,69 @@
+<?php
+
+namespace App\Http\Controllers\Api\Posts;
+
+use App\Http\Controllers\Controller;
+use App\Models\Post;
+use App\Models\PostSave;
+use App\Services\Posts\PostCountersService;
+use App\Services\Posts\PostFeedService;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+
+/**
+ * POST   /api/posts/{id}/save
+ * DELETE /api/posts/{id}/save
+ * GET    /api/posts/saved
+ */
+class PostSaveController extends Controller
+{
+    public function __construct(
+        private PostCountersService $counters,
+        private PostFeedService     $feedService,
+    ) {}
+
+    public function save(Request $request, int $id): JsonResponse
+    {
+        $post = Post::where('status', Post::STATUS_PUBLISHED)->findOrFail($id);
+        $user = $request->user();
+
+        if (PostSave::where('post_id', $post->id)->where('user_id', $user->id)->exists()) {
+            return response()->json(['message' => 'Already saved.', 'saved' => true], 200);
+        }
+
+        PostSave::create(['post_id' => $post->id, 'user_id' => $user->id]);
+        $this->counters->incrementSaves($post);
+
+        return response()->json(['message' => 'Post saved.', 'saved' => true, 'saves_count' => $post->fresh()->saves_count]);
+    }
+
+    public function unsave(Request $request, int $id): JsonResponse
+    {
+        $post   = Post::findOrFail($id);
+        $user   = $request->user();
+        $save   = PostSave::where('post_id', $post->id)->where('user_id', $user->id)->first();
+
+        if (! $save) {
+            return response()->json(['message' => 'Not saved.', 'saved' => false], 200);
+        }
+
+        $save->delete();
+        $this->counters->decrementSaves($post);
+
+        return response()->json(['message' => 'Post unsaved.', 'saved' => false, 'saves_count' => $post->fresh()->saves_count]);
+    }
+
+    public function index(Request $request): JsonResponse
+    {
+        $user   = $request->user();
+        $page   = max(1, (int) $request->query('page', 1));
+        $result = $this->feedService->getSavedFeed($user, $page);
+
+        $formatted = array_map(
+            fn ($post) => $this->feedService->formatPost($post, $user->id),
+            $result['data'],
+        );
+
+        return response()->json(['data' => array_values($formatted), 'meta' => $result['meta']]);
+    }
+}