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/css/app.css

@@ -87,3 +87,107 @@
   }
 }
 
+/* ─── TipTap rich text editor ─── */
+.tiptap {
+  outline: none;
+}
+
+.tiptap p.is-editor-empty:first-child::before {
+  content: attr(data-placeholder);
+  float: left;
+  color: theme('colors.zinc.600');
+  pointer-events: none;
+  height: 0;
+}
+
+.tiptap img {
+  max-width: 100%;
+  height: auto;
+  border-radius: 0.75rem;
+}
+
+.tiptap pre {
+  background: theme('colors.white / 4%');
+  border: 1px solid theme('colors.white / 6%');
+  border-radius: 0.75rem;
+  padding: 0.75rem 1rem;
+  overflow-x: auto;
+}
+
+.tiptap pre code {
+  background: none;
+  border: none;
+  padding: 0;
+  font-size: 0.8125rem;
+  color: theme('colors.zinc.300');
+}
+
+.tiptap blockquote {
+  border-left: 3px solid theme('colors.sky.500 / 40%');
+  padding-left: 1rem;
+  margin-left: 0;
+  color: theme('colors.zinc.400');
+  font-style: italic;
+}
+
+.tiptap hr {
+  border: none;
+  border-top: 1px solid theme('colors.white / 10%');
+  margin: 1.5rem 0;
+}
+
+.tiptap ul {
+  list-style-type: disc;
+  padding-left: 1.5rem;
+}
+
+.tiptap ol {
+  list-style-type: decimal;
+  padding-left: 1.5rem;
+}
+
+.tiptap li {
+  margin-bottom: 0.25rem;
+}
+
+.tiptap a {
+  color: theme('colors.sky.300');
+  text-decoration: underline;
+  text-underline-offset: 2px;
+}
+
+.tiptap a:hover {
+  color: theme('colors.sky.200');
+}
+
+/* ─── @mention pills ─── */
+.tiptap .mention,
+.mention {
+  background: theme('colors.sky.500 / 15%');
+  color: theme('colors.sky.300');
+  border-radius: 0.375rem;
+  padding: 0.125rem 0.375rem;
+  font-weight: 500;
+  font-size: 0.875rem;
+  text-decoration: none;
+  cursor: pointer;
+  white-space: nowrap;
+}
+
+.tiptap .mention:hover {
+  background: theme('colors.sky.500 / 25%');
+  color: theme('colors.sky.200');
+}
+
+/* ─── Tippy.js mention dropdown theme ─── */
+.tippy-box[data-theme~='mention'] {
+  background: transparent;
+  border: none;
+  padding: 0;
+  box-shadow: none;
+}
+
+.tippy-box[data-theme~='mention'] .tippy-content {
+  padding: 0;
+}
+