refactor(rename): handler functions, routes, legacy 301 redirects

Second rename pass closing the backend cleanup:

* handler functions (handleListProjekte, handleCreateFrist, …) renamed
  to English equivalents so every symbol in the handler package matches
  the URL/entity it serves.
* services.FristStatusFilter + filter constants renamed to
  DeadlineStatusFilter / DeadlineFilterOverdue etc.
* services.TerminListFilter / TerminCalDAVPusher / TerminSummaryCounts
  renamed to AppointmentListFilter / AppointmentCalDAVPusher /
  AppointmentSummaryCounts.
* GlossarTerm/GlossarSuggestion/glossarTerms → Glossary*.
* CourtsFeedback/CourtsResponse (formerly Gerichte*).
* handlers.Services.{Projekt,Parteien,Frist,Termin,Notiz,Dezernat} →
  {Project,Party,Deadline,Appointment,Note,Department}; dbServices
  struct + consumers likewise.
* email templates: {{.FristURL}} → {{.DeadlineURL}}, {{.FristenURL}} →
  {{.DeadlinesURL}}.
* links.go category IDs: gerichte → courts.
* cmd/server/main.go local vars: projektSvc/terminSvc/dezernatSvc →
  projectSvc/appointmentSvc/departmentSvc.

Routes:
* removed all /api/akten alias routes (API clients use /api/projects now).
* removed /api/akten/*/deadlines, /*/notes, /*/parties, /*/appointments,
  /*/checklists, /*/events, /*/summary alias variants.
* new internal/handlers/redirects.go registers 301 Moved Permanently
  redirects for every legacy German GET path: /akten, /projekte, /fristen,
  /termine, /notizen, /einstellungen, /checklisten, /dezernate, /parteien,
  /gerichte, /glossar. Sub-paths + query strings are preserved so old
  bookmarks keep working.

Kept in German (product names, per task spec):
* /tools/fristenrechner, /tools/kostenrechner, /tools/gebuehrentabellen
* FristenrechnerService / KostenrechnerService types
* User.Dezernat + paliad.users.dezernat free-text legacy column (separate
  from the new paliad.departments entity).

go build / vet / test clean.

cmd/server/main.go

@@ -52,7 +52,7 @@ func main() {
 
 	// DATABASE_URL is optional during the Phase A → Phase D transition. The
 	// existing knowledge-platform features (Kostenrechner, Glossar, etc.) work
-	// without a DB. Akten/Deadline endpoints return 503 until DATABASE_URL is set.
+	// without a DB. matter-management endpoints return 503 until DATABASE_URL is set.
 	dbURL := os.Getenv("DATABASE_URL")
 	var svcBundle *handlers.Services
 	var caldavSvc *services.CalDAVService
@@ -70,9 +70,9 @@ func main() {
 		}
 		holidays := services.NewHolidayService(pool)
 		users := services.NewUserService(pool)
-		projektSvc := services.NewProjectService(pool, users)
-		teamSvc := services.NewTeamService(pool, projektSvc)
-		dezernatSvc := services.NewDepartmentService(pool, users)
+		projectSvc := services.NewProjectService(pool, users)
+		teamSvc := services.NewTeamService(pool, projectSvc)
+		departmentSvc := services.NewDepartmentService(pool, users)
 		rules := services.NewDeadlineRuleService(pool)
 
 		// Phase F: optional CalDAV cipher. If CALDAV_ENCRYPTION_KEY is unset
@@ -89,31 +89,31 @@ func main() {
 			log.Println("CalDAV encryption configured (AES-256-GCM)")
 		}
 
-		terminSvc := services.NewAppointmentService(pool, projektSvc)
-		caldavSvc = services.NewCalDAVService(pool, cipher, terminSvc)
+		appointmentSvc := services.NewAppointmentService(pool, projectSvc)
+		caldavSvc = services.NewCalDAVService(pool, cipher, appointmentSvc)
 		// Wire the push hook so user-driven mutations sync to the external
 		// calendar without waiting for the next 60-second tick.
-		terminSvc.SetCalDAVPusher(caldavSvc)
+		appointmentSvc.SetCalDAVPusher(caldavSvc)
 
 		baseURL := os.Getenv("PALIAD_BASE_URL")
 		inviteSvc := services.NewInviteService(pool, mailSvc, handlers.AllowedEmailDomains, baseURL)
 		reminderSvc := services.NewReminderService(pool, mailSvc, users, baseURL)
 
 		svcBundle = &handlers.Services{
-			Project:        projektSvc,
+			Project:        projectSvc,
 			Team:           teamSvc,
-			Dezernat:       dezernatSvc,
-			Parties:       services.NewPartyService(pool, projektSvc),
-			Deadline:          services.NewDeadlineService(pool, projektSvc),
-			Appointment:         terminSvc,
+			Department:     departmentSvc,
+			Party:          services.NewPartyService(pool, projectSvc),
+			Deadline:       services.NewDeadlineService(pool, projectSvc),
+			Appointment:    appointmentSvc,
 			CalDAV:         caldavSvc,
 			Rules:          rules,
 			Calculator:     services.NewDeadlineCalculator(holidays),
 			Users:          users,
 			Fristenrechner: services.NewFristenrechnerService(rules, holidays),
 			Dashboard:      services.NewDashboardService(pool, users),
-			Note:          services.NewNoteService(pool, projektSvc, terminSvc),
-			ChecklistInst:  services.NewChecklistInstanceService(pool, projektSvc),
+			Note:           services.NewNoteService(pool, projectSvc, appointmentSvc),
+			ChecklistInst:  services.NewChecklistInstanceService(pool, projectSvc),
 			Mail:           mailSvc,
 			Invite:         inviteSvc,
 		}
@@ -132,7 +132,7 @@ func main() {
 			caldavSvc.Stop()
 		}()
 	} else {
-		log.Println("DATABASE_URL not set — Akten/Deadline endpoints will return 503")
+		log.Println("DATABASE_URL not set — matter-management endpoints will return 503")
 	}
 
 	mux := http.NewServeMux()