Codebase audit: remove dead code, fix broken patterns, consolidate duplicates; v2.0.27

- Remove unused prop-types dep, deprecated useOutboundLinkTracking export
- Fix missing linkClicks key in analyticsEvents initial state (B-01)
- Export ADMIN_SESSION_COOKIE from auth.js; remove local copy in admin-auth.js (D-02)
- Remove cookieFlags() wrapper in auth.js and study-helpers.js; use cookieSecureFlag() directly (U-04)
- Remove ADMIN_SESSION_TTL_MS duplicate from config.js (D-01)
- Remove DEFAULT_SEO/DEFAULT_LEGAL/DEFAULT_REDIRECT_RULES/DEFAULT_PODCAST_FEATURED_LINKS/DEFAULT_PUBLISH_STATE
  duplicates from config.js; re-export from helpers.js (D-04, fixes sitemapPaths divergence)
- Fix email.js hardcoded fallback strings to use DEFAULT_RESEND_TO/DEFAULT_RESEND_REPLY_TO (M-02)
- Remove duplicate normalizeIp, isPrivateOrLocalIp, normalizeRedirectPath, sanitizeUrl,
  sanitizeRedirectRules bodies from study-helpers.js; re-export from helpers.js (D-03)
- Fix pruneStatsByDays to import VISITOR_RETENTION_DAYS_DEFAULT from config.js (B-02)
- Fix createTitusDownloadToken to use DOWNLOAD_TOKEN_TTL_MS constant (B-03)
- Remove normalizeMessageType duplicate from study-helpers.js (U-03/D-08)
- Remove dead wantsWelcome variable in contact.js; use shouldSendWelcome (B-04)
- Replace dynamic imports in contact.js with static imports (B-07)
- Remove dead wantsWelcome=true in study-auth.js (B-05)
- Merge duplicate import blocks in analytics.js and public.js (D-05, D-06)
- Replace dynamic readFile re-import in nuggets-host-upload.js (B-06)
- Replace hardcoded SITE_URL fallbacks with getCanonicalBaseUrl() (M-06)
- Replace raw resend.emails.send in study-account.js with sendResendEmailWithRetry (M-01)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "2.0.26",
+  "version": "2.0.27",
   "type": "module",
   "scripts": {
     "dev": "vite",
@@ -26,7 +26,6 @@
     "mammoth": "^1.12.0",
     "multer": "^2.3.0",
     "otplib": "^13.4.0",
-    "prop-types": "^15.8.1",
     "qrcode": "^1.5.4",
     "react": "^19.2.4",
     "react-chartjs-2": "^5.2.0",