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)

app/sites/[id]/page.tsx

@@ -17,7 +17,7 @@ import {
   type Stats,
   type DailyStat,
 } from '@/lib/api/stats'
-import { getDateRange, formatDate } from '@ciphera-net/ui'
+import { getDateRange, formatDate, getThisWeekRange, getThisMonthRange } from '@/lib/utils/dateRanges'
 import { toast } from '@ciphera-net/ui'
 import { Button } from '@ciphera-net/ui'
 import { Select, DatePicker, DownloadIcon } from '@ciphera-net/ui'
@@ -63,19 +63,6 @@ function loadSavedSettings(): {
   }
 }
 
-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) }
-}
-
-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) }
-}
 
 function getInitialDateRange(): { start: string; end: string } {
   const settings = loadSavedSettings()
@@ -442,7 +429,7 @@ export default function SiteDashboardPage() {
         <div className="flex items-center justify-between mb-3">
           <div className="flex items-center gap-4">
             <div>
-              <h1 className="text-2xl font-bold text-neutral-900 dark:text-white mb-1">
+              <h1 className="text-2xl font-bold text-white mb-1">
                 {site.name}
               </h1>
               <p className="text-neutral-600 dark:text-neutral-400">