feat(customers): full CRUD module — pattern for all other modules

Establishes the multi-tenant module pattern. Subsequent modules (services,
software, calendar, tasks, finance, invoices) will copy this structure.

Validation:
- lib/validation/customers.ts: Zod schema with Turkish messages, optional
  fields normalized to undefined.

Server actions (lib/appwrite/customer-actions.ts):
- createCustomerAction, updateCustomerAction, deleteCustomerAction
- All call requireTenant() guard, write team-scoped row permissions
  (read+update by team, delete by owner|admin), and emit audit log.
- Update/delete cross-check tenantId on the existing row before mutating
  (defense in depth even though row-level perms already enforce it).
- Field-level errors flattened from Zod for inline form display.

Server-side queries (lib/appwrite/customer-queries.ts):
- listCustomers(tenantId), getCustomer(tenantId, id) — admin SDK with
  Query.equal('tenantId',...) tenant scope.

UI:
- /customers page (server component): pulls active tenant context, lists
  customers, hands off to CustomersClient.
- CustomersClient: TanStack Table with global filter (name/email/phone/
  taxId), column sorting on name + createdAt, pagination (20/page),
  status badges, row actions (Edit/Delete dropdown), empty-state CTA.
- CustomerFormSheet: shadcn Sheet-based add/edit form with all fields,
  toast feedback (sonner), inline field errors. Reused for create + update
  by switching the action.
- DeleteCustomerDialog: confirmation modal with destructive button.

Infrastructure:
- Added sonner Toaster to root layout (richColors, closeButton).
- Updated metadata to 'İşletmem KovakCRM' and html lang='tr'.
- Renamed theme storage key to isletmem-ui-theme.

src/lib/appwrite/customer-actions.ts

@@ -0,0 +1,185 @@
+"use server";
+
+import { revalidatePath } from "next/cache";
+import { AppwriteException, ID, Permission, Role } from "node-appwrite";
+import { z } from "zod";
+
+import { logAudit } from "./audit";
+import { DATABASE_ID, TABLES, type Customer } from "./schema";
+import { createAdminClient } from "./server";
+import { requireTenant } from "./tenant-guard";
+import type { CustomerActionState } from "./customer-types";
+import { customerSchema } from "@/lib/validation/customers";
+
+function appwriteError(e: unknown): string {
+  if (e instanceof AppwriteException) {
+    return e.message || "Beklenmeyen bir hata oluştu.";
+  }
+  return "Bağlantı hatası. Tekrar deneyin.";
+}
+
+function pickFormFields(formData: FormData) {
+  return {
+    name: String(formData.get("name") ?? "").trim(),
+    email: String(formData.get("email") ?? "").trim(),
+    phone: String(formData.get("phone") ?? "").trim(),
+    taxId: String(formData.get("taxId") ?? "").trim(),
+    address: String(formData.get("address") ?? "").trim(),
+    notes: String(formData.get("notes") ?? "").trim(),
+    status: (formData.get("status") as "active" | "passive" | null) ?? "active",
+  };
+}
+
+function flattenErrors(err: z.ZodError): Record<string, string> {
+  const out: Record<string, string> = {};
+  for (const issue of err.issues) {
+    const key = issue.path.join(".");
+    if (key && !out[key]) out[key] = issue.message;
+  }
+  return out;
+}
+
+function teamRowPermissions(tenantId: string) {
+  return [
+    Permission.read(Role.team(tenantId)),
+    Permission.update(Role.team(tenantId)),
+    Permission.delete(Role.team(tenantId, "owner")),
+    Permission.delete(Role.team(tenantId, "admin")),
+  ];
+}
+
+export async function createCustomerAction(
+  _prev: CustomerActionState,
+  formData: FormData,
+): Promise<CustomerActionState> {
+  let ctx;
+  try {
+    ctx = await requireTenant();
+  } catch {
+    return { ok: false, error: "Yetkiniz yok." };
+  }
+
+  const parsed = customerSchema.safeParse(pickFormFields(formData));
+  if (!parsed.success) {
+    return { ok: false, error: "Form geçersiz.", fieldErrors: flattenErrors(parsed.error) };
+  }
+
+  try {
+    const { tablesDB } = createAdminClient();
+    const row = await tablesDB.createRow(
+      DATABASE_ID,
+      TABLES.customers,
+      ID.unique(),
+      {
+        tenantId: ctx.tenantId,
+        createdBy: ctx.user.id,
+        ...parsed.data,
+      },
+      teamRowPermissions(ctx.tenantId),
+    );
+
+    await logAudit({
+      tenantId: ctx.tenantId,
+      userId: ctx.user.id,
+      action: "create",
+      entityType: "customer",
+      entityId: row.$id,
+      changes: parsed.data,
+    });
+  } catch (e) {
+    return { ok: false, error: appwriteError(e) };
+  }
+
+  revalidatePath("/customers");
+  return { ok: true };
+}
+
+export async function updateCustomerAction(
+  _prev: CustomerActionState,
+  formData: FormData,
+): Promise<CustomerActionState> {
+  const id = String(formData.get("id") ?? "");
+  if (!id) return { ok: false, error: "ID eksik." };
+
+  let ctx;
+  try {
+    ctx = await requireTenant();
+  } catch {
+    return { ok: false, error: "Yetkiniz yok." };
+  }
+
+  const parsed = customerSchema.safeParse(pickFormFields(formData));
+  if (!parsed.success) {
+    return { ok: false, error: "Form geçersiz.", fieldErrors: flattenErrors(parsed.error) };
+  }
+
+  try {
+    const { tablesDB } = createAdminClient();
+    const existing = (await tablesDB.getRow(
+      DATABASE_ID,
+      TABLES.customers,
+      id,
+    )) as unknown as Customer;
+
+    if (existing.tenantId !== ctx.tenantId) {
+      return { ok: false, error: "Erişim engellendi." };
+    }
+
+    await tablesDB.updateRow(DATABASE_ID, TABLES.customers, id, parsed.data);
+
+    await logAudit({
+      tenantId: ctx.tenantId,
+      userId: ctx.user.id,
+      action: "update",
+      entityType: "customer",
+      entityId: id,
+      changes: parsed.data,
+    });
+  } catch (e) {
+    return { ok: false, error: appwriteError(e) };
+  }
+
+  revalidatePath("/customers");
+  return { ok: true };
+}
+
+export async function deleteCustomerAction(formData: FormData): Promise<CustomerActionState> {
+  const id = String(formData.get("id") ?? "");
+  if (!id) return { ok: false, error: "ID eksik." };
+
+  let ctx;
+  try {
+    ctx = await requireTenant();
+  } catch {
+    return { ok: false, error: "Yetkiniz yok." };
+  }
+
+  try {
+    const { tablesDB } = createAdminClient();
+    const existing = (await tablesDB.getRow(
+      DATABASE_ID,
+      TABLES.customers,
+      id,
+    )) as unknown as Customer;
+
+    if (existing.tenantId !== ctx.tenantId) {
+      return { ok: false, error: "Erişim engellendi." };
+    }
+
+    await tablesDB.deleteRow(DATABASE_ID, TABLES.customers, id);
+
+    await logAudit({
+      tenantId: ctx.tenantId,
+      userId: ctx.user.id,
+      action: "delete",
+      entityType: "customer",
+      entityId: id,
+      changes: { name: existing.name },
+    });
+  } catch (e) {
+    return { ok: false, error: appwriteError(e) };
+  }
+
+  revalidatePath("/customers");
+  return { ok: true };
+}