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

resources/js/components/profile/tabs/TabCollections.jsx

@@ -0,0 +1,65 @@
+import React from 'react'
+
+/**
+ * TabCollections
+ * Collections feature placeholder.
+ */
+export default function TabCollections({ collections }) {
+  if (collections?.length > 0) {
+    return (
+      <div
+        id="tabpanel-collections"
+        role="tabpanel"
+        aria-labelledby="tab-collections"
+        className="pt-6"
+      >
+        <div className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4">
+          {collections.map((col) => (
+            <div
+              key={col.id}
+              className="bg-white/4 ring-1 ring-white/10 rounded-2xl overflow-hidden group hover:ring-sky-400/30 transition-all cursor-pointer shadow-xl shadow-black/20"
+            >
+              {col.cover_image ? (
+                <div className="aspect-video overflow-hidden bg-black/30">
+                  <img
+                    src={col.cover_image}
+                    alt={col.title}
+                    className="w-full h-full object-cover transition-transform duration-300 group-hover:scale-105"
+                    loading="lazy"
+                  />
+                </div>
+              ) : (
+                <div className="aspect-video bg-white/5 flex items-center justify-center text-slate-600">
+                  <i className="fa-solid fa-layer-group text-3xl" />
+                </div>
+              )}
+              <div className="p-4">
+                <h3 className="font-semibold text-white truncate">{col.title}</h3>
+                <p className="text-sm text-slate-500 mt-0.5">{col.items_count ?? 0} artworks</p>
+              </div>
+            </div>
+          ))}
+        </div>
+      </div>
+    )
+  }
+
+  return (
+    <div
+      id="tabpanel-collections"
+      role="tabpanel"
+      aria-labelledby="tab-collections"
+      className="pt-6"
+    >
+      <div className="bg-white/4 ring-1 ring-white/10 rounded-2xl px-8 py-16 text-center shadow-xl shadow-black/20 backdrop-blur">
+        <div className="w-20 h-20 rounded-2xl bg-white/5 flex items-center justify-center mx-auto mb-5 text-slate-500">
+          <i className="fa-solid fa-layer-group text-3xl" />
+        </div>
+        <h3 className="text-lg font-bold text-white mb-2">Collections Coming Soon</h3>
+        <p className="text-slate-500 text-sm max-w-sm mx-auto">
+          Group artworks into curated collections. This feature is currently in development.
+        </p>
+      </div>
+    </div>
+  )
+}