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)

lib/utils/dateRanges.ts

@@ -0,0 +1,20 @@
+import { getDateRange, formatDate } from '@ciphera-net/ui'
+
+/** Monday–today range for "This week" option */
+export function getThisWeekRange(): { start: string; end: string } {
+  const today = new Date()
+  const dayOfWeek = today.getDay()
+  const monday = new Date(today)
+  monday.setDate(today.getDate() - (dayOfWeek === 0 ? 6 : dayOfWeek - 1))
+  return { start: formatDate(monday), end: formatDate(today) }
+}
+
+/** 1st of month–today range for "This month" option */
+export function getThisMonthRange(): { start: string; end: string } {
+  const today = new Date()
+  const firstOfMonth = new Date(today.getFullYear(), today.getMonth(), 1)
+  return { start: formatDate(firstOfMonth), end: formatDate(today) }
+}
+
+// Re-export for convenience
+export { getDateRange, formatDate }