feat(banking C): credit cards + monthly statements

Final banking step. User-managed: each month, paste your bank statement
totals into the form. We don't auto-compute interest — bank's number is
authoritative.

Schema:
- credit_cards: bankName, cardName, last4, creditLimit, statementDay,
  dueDay, interestRate (monthly nominal %), bankAccountId (optional FK,
  payments expense from this account), archived, notes.
- credit_card_statements: cardId, period (YYYY-MM), statementDate,
  dueDate, totalDebt, minimumPayment, paidAmount, status
  (pending/partial/paid/overdue), financeEntryId (link to last payment).
- Indexes on (tenantId, archived) for cards and (tenantId, cardId) +
  (tenantId, status, dueDate) for statements.

Server (lib/appwrite/credit-card-actions.ts):
- create/update/archive(toggle)/delete for cards. Card delete cascades
  through statements + their finance_entries.
- createStatementAction: computes status from dueDate + paidAmount.
- payStatementAction: partial-payment friendly. Creates a single
  finance_entry expense for the pay amount, capped at remaining balance,
  bankAccountId carried from the card. Recomputes status: paid (full),
  partial (some + pre-due), overdue (past due with anything < total).
- deleteStatementAction: removes linked finance_entry too.
- All audit-logged.

UI (/finance/cards):
- 3 stat cards: aktif kart sayısı, bekleyen toplam, vadesi geçmiş ekstre.
- Per-card panel: bank/name/last4, limit + statement/due day + monthly
  interest, current outstanding. Statement table inside card with status
  badges, Öde button (opens partial-payment dialog), delete button.
- CardFormSheet for card CRUD, StatementFormSheet for statement creation
  with default period/dates derived from card's statementDay/dueDay.

Sidebar Finans submenu now functional: Banka hesapları → /finance/banks,
Krediler → /finance/loans, Kredi kartları → /finance/cards.

src/lib/validation/credit-cards.ts

@@ -0,0 +1,73 @@
+import { z } from "zod";
+
+export const creditCardSchema = z.object({
+  bankName: z.string().trim().min(1, "Banka adı zorunlu.").max(100),
+  cardName: z.string().trim().min(1, "Kart adı zorunlu.").max(100),
+  last4: z
+    .string()
+    .trim()
+    .max(4)
+    .optional()
+    .transform((v) => (v ? v.replace(/\D/g, "").slice(-4) : undefined)),
+  creditLimit: z
+    .union([z.number(), z.string()])
+    .optional()
+    .transform((v) => {
+      if (v === undefined || v === "") return 0;
+      const n = typeof v === "string" ? Number(v.replace(",", ".")) : v;
+      return Number.isFinite(n) ? n : 0;
+    }),
+  statementDay: z
+    .union([z.number(), z.string()])
+    .optional()
+    .transform((v) => {
+      if (v === undefined || v === "") return 1;
+      const n = typeof v === "string" ? parseInt(v, 10) : v;
+      return Number.isFinite(n) ? Math.min(28, Math.max(1, n)) : 1;
+    }),
+  dueDay: z
+    .union([z.number(), z.string()])
+    .optional()
+    .transform((v) => {
+      if (v === undefined || v === "") return 10;
+      const n = typeof v === "string" ? parseInt(v, 10) : v;
+      return Number.isFinite(n) ? Math.min(28, Math.max(1, n)) : 10;
+    }),
+  interestRate: z
+    .union([z.number(), z.string()])
+    .optional()
+    .transform((v) => {
+      if (v === undefined || v === "") return 4.25;
+      const n = typeof v === "string" ? Number(v.replace(",", ".")) : v;
+      return Number.isFinite(n) ? n : 4.25;
+    }),
+  bankAccountId: z.string().optional().transform((v) => (v ? v : undefined)),
+  notes: z.string().trim().max(500).optional().transform((v) => (v ? v : undefined)),
+});
+
+export type CreditCardInput = z.infer<typeof creditCardSchema>;
+
+export const statementSchema = z.object({
+  cardId: z.string().min(1, "Kart seçin."),
+  period: z
+    .string()
+    .regex(/^\d{4}-\d{2}$/, "Dönem YYYY-AA formatında olmalı.")
+    .max(7),
+  statementDate: z.string().min(1, "Hesap kesim tarihi zorunlu."),
+  dueDate: z.string().min(1, "Son ödeme tarihi zorunlu."),
+  totalDebt: z
+    .union([z.number(), z.string()])
+    .transform((v) => (typeof v === "string" ? Number(v.replace(",", ".")) : v))
+    .pipe(z.number().nonnegative("Negatif olamaz.")),
+  minimumPayment: z
+    .union([z.number(), z.string()])
+    .optional()
+    .transform((v) => {
+      if (v === undefined || v === "") return 0;
+      const n = typeof v === "string" ? Number(v.replace(",", ".")) : v;
+      return Number.isFinite(n) ? n : 0;
+    }),
+  notes: z.string().trim().max(500).optional().transform((v) => (v ? v : undefined)),
+});
+
+export type StatementInput = z.infer<typeof statementSchema>;