feat(dönem): dönem kapatma, devir ve düzeltme için yeniden açma (backend)

- POST /periods/{id}/close: tek transaction; açık → borç, artı → birikim + devir
- Devir sonraki dönem açılınca ona bağlanır
- POST /periods/{id}/reopen (sahip): düzeltme modu, yeni dönem açık kalır

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/lib/plan-draft.test.ts

@@ -14,6 +14,8 @@ const period: Period = {
   status: 'open',
   savings_goal: 500_000,
   reflection_md: null,
+  to_savings: null,
+  closed_at: null,
   version: 3,
   weeks: [
     { index: 1, start_date: '2026-12-01', last_date: '2026-12-06', days: 6 },

frontend/src/types/Carryover.ts

@@ -0,0 +1,11 @@
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+
+export type Carryover = { 
+/**
+ * `debt` (borç) · `surplus` (artı)
+ */
+kind: "debt" | "surplus", amount: number, 
+/**
+ * Sonraki dönem henüz açılmadıysa `null` (açılınca bağlanır)
+ */
+to_period_id: string | null, };

frontend/src/types/Period.ts

@@ -22,4 +22,12 @@ savings_goal: number,
 /**
  * "Nasıl daha iyi yapabilirim?" (Markdown)
  */
-reflection_md: string | null, version: number, weeks: Array<PeriodWeek>, };
+reflection_md: string | null, 
+/**
+ * Kapanışta birikime aktarılan (kuruş); kapanmamışsa `null`
+ */
+to_savings: number | null, 
+/**
+ * Kapanış zamanı (ISO 8601)
+ */
+closed_at: string | null, version: number, weeks: Array<PeriodWeek>, };

frontend/src/types/PeriodCloseRequest.ts

@@ -0,0 +1,7 @@
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+
+export type PeriodCloseRequest = { 
+/**
+ * Birikime aktarılacak (kuruş); verilmezse gerçekleşen birikimin tamamı. Kalanı artı olarak devreder.
+ */
+to_savings?: number, version?: number, };

frontend/src/types/PeriodCloseResult.ts

@@ -0,0 +1,13 @@
+// This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
+import type { Carryover } from "./Carryover";
+import type { Period } from "./Period";
+
+export type PeriodCloseResult = { period: Period, 
+/**
+ * Değerlendirmenin 4. sorusu (negatifse açık)
+ */
+realized_savings: number, to_savings: number, 
+/**
+ * Sonraki döneme devreden; yoksa `null`
+ */
+carryover: Carryover | null, };

frontend/src/types/PeriodStatus.ts

@@ -1,3 +1,3 @@
 // This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
 
-export type PeriodStatus = "open" | "closed";
+export type PeriodStatus = "open" | "closed" | "correcting";