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/lib/uploadNotices.js

@@ -0,0 +1,71 @@
+const REASON_MAP = {
+  duplicate_hash: {
+    type: 'error',
+    message: 'This file already exists in Skinbase. Please upload a different file.',
+  },
+  validation_failed: {
+    type: 'error',
+    message: 'Upload validation failed. Please check the file and try again.',
+  },
+  scan_failed: {
+    type: 'error',
+    message: 'Upload scan failed. Please try another file.',
+  },
+  quota_exceeded: {
+    type: 'warning',
+    message: 'Upload limit reached. Please wait before uploading again.',
+  },
+}
+
+function normalizeType(value, fallback = 'error') {
+  const normalized = String(value || '').toLowerCase()
+  if (normalized === 'success' || normalized === 'warning' || normalized === 'error') return normalized
+  return fallback
+}
+
+export function mapUploadErrorNotice(error, fallback = 'Upload failed.') {
+  const status = Number(error?.response?.status || 0)
+  const payload = error?.response?.data || {}
+  const reason = String(payload?.reason || '').toLowerCase()
+  const mapped = REASON_MAP[reason]
+
+  const type = mapped?.type
+    ? mapped.type
+    : normalizeType(payload?.type || payload?.level, status >= 500 ? 'error' : 'warning')
+
+  const message =
+    mapped?.message ||
+    (typeof payload?.message === 'string' && payload.message.trim()) ||
+    (typeof error?.message === 'string' && error.message.trim()) ||
+    fallback
+
+  return {
+    type,
+    message,
+    reason,
+    status,
+  }
+}
+
+export function mapUploadResultNotice(payload, options = {}) {
+  const {
+    fallbackType = 'success',
+    fallbackMessage = 'Operation completed successfully.',
+  } = options
+
+  const reason = String(payload?.reason || '').toLowerCase()
+  const mapped = REASON_MAP[reason]
+
+  const type = mapped?.type || normalizeType(payload?.type || payload?.level, fallbackType)
+  const message =
+    mapped?.message ||
+    (typeof payload?.message === 'string' && payload.message.trim()) ||
+    fallbackMessage
+
+  return {
+    type,
+    message,
+    reason,
+    status: Number(payload?.status_code || 0),
+  }
+}