feat: Phase C — Fristenrechner → DB-backed via FristenrechnerService

- Delete internal/calc/deadlines.go/deadline_rules.go/holidays.go (ported to services)
- fristenrechner handler routes through FristenrechnerService when pool present
- Returns 503 with German message when DATABASE_URL unset (page still renders)
- Migration 012: add name_en columns + seed 9 UI-facing proceeding types
- Commit captures cronus's work after session termination

cmd/server/main.go

@@ -49,12 +49,14 @@ func main() {
 		holidays := services.NewHolidayService(pool)
 		users := services.NewUserService(pool)
 		akteSvc := services.NewAkteService(pool, users)
+		rules := services.NewDeadlineRuleService(pool)
 		svcBundle = &handlers.Services{
-			Akte:       akteSvc,
-			Parteien:   services.NewParteienService(pool, akteSvc),
-			Rules:      services.NewDeadlineRuleService(pool),
-			Calculator: services.NewDeadlineCalculator(holidays),
-			Users:      users,
+			Akte:           akteSvc,
+			Parteien:       services.NewParteienService(pool, akteSvc),
+			Rules:          rules,
+			Calculator:     services.NewDeadlineCalculator(holidays),
+			Users:          users,
+			Fristenrechner: services.NewFristenrechnerService(rules, holidays),
 		}
 		log.Println("Phase B services initialised")
 	} else {