Add biweekly pay schedule with projected paychecks and dashboard integration

- Add PaySchedule model (anchorDate + amountCents + active flag)
- Add /pay-schedule API route (GET, POST, DELETE)
- Project biweekly pay dates from anchor; deduplicate against manual paychecks
- Merge projected paychecks into dashboard totals and daily chart
- Fix DST day-shift bug in getProjectedPayDates by using Date.UTC throughout
- Rewrite paycheck workspace: schedule panel at top, manual entry below,
  projected dates with "Mark received" buttons, confirmed badges
- Pass paySchedule context to Ollama insight prompt

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

prisma/schema.prisma

@@ -34,6 +34,14 @@ model Paycheck {
   createdAt   DateTime @default(now())
 }
 
+model PaySchedule {
+  id          String   @id @default(cuid())
+  amountCents Int
+  anchorDate  String
+  active      Boolean  @default(true)
+  createdAt   DateTime @default(now())
+}
+
 model MonthlyInsight {
   id              String   @id @default(cuid())
   month           String   @unique