fix: frontend consistency audit — 55 files cleaned up

Consistency fixes:
- Extract getThisWeekRange/getThisMonthRange to shared lib/utils/dateRanges.ts
  (removed 4 identical copy-pasted definitions)
- Add error boundaries for behavior, cdn, search, pagespeed pages
  (4 new error.tsx files — previously fell through to generic parent error)
- Add "View setup guide" CTA to empty states on journeys and behavior pages
  (previously showed text with no actionable button)
- Fix non-lazy useState initializer in funnel detail page
- Fix Bot & Spam settings header from text-xl to text-2xl (matches all other sections)
- Add useMinimumLoading to PageSpeed skeleton (consistent with all other pages)

Cleanup:
- Remove 438 redundant dark: class prefixes (app is dark-mode only)
  text-neutral-500 dark:text-neutral-400 → text-neutral-400 (206 occurrences)
  text-neutral-900 dark:text-white → text-white (232 occurrences)
- Remove dead @stripe/react-stripe-js and @stripe/stripe-js packages
  (billing migrated to Polar, no code imports Stripe)
- Remove duplicate motion package (framer-motion is the one actually used)

package.json

@@ -20,8 +20,6 @@
     "@radix-ui/react-navigation-menu": "^1.2.14",
     "@radix-ui/react-slot": "^1.2.4",
     "@simplewebauthn/browser": "^13.2.2",
-    "@stripe/react-stripe-js": "^5.6.0",
-    "@stripe/stripe-js": "^8.7.0",
     "@tanstack/react-virtual": "^3.13.21",
     "@types/d3": "^7.4.3",
     "@visx/curve": "^3.12.0",
@@ -44,7 +42,6 @@
     "jspdf": "^4.0.0",
     "jspdf-autotable": "^5.0.7",
     "lucide-react": "^0.577.0",
-    "motion": "^12.35.2",
     "next": "^16.1.1",
     "radix-ui": "^1.4.3",
     "react": "^19.2.3",