feat: username/password authentication for admin and merchant panels

- Add PasswordHasher utility (PBKDF2/SHA-256, 100k iterations)
- Add Username + PasswordHash fields to Employee and SystemAdmin entities
- EF migration: AddPasswordLogin (nullable columns on both tables)
- Meezi.API: POST /api/auth/login (employee password login, CHOOSE_CAFE support)
- Meezi.API: PUT/DELETE /api/cafes/{id}/employees/{id}/credentials (Owner/Manager only)
- Meezi.Admin.API: POST /api/admin/auth/login + PUT /api/admin/auth/password
- Dashboard login page: OTP / Password tabs
- Admin login page: OTP / Password tabs
- HR screen: new Credentials tab for setting employee username/password
- PlatformDataSeeder: ensure system admin + integration settings in production
- Trial countdown banner: updated deadline to 1 Tir 1405 (Jun 22)
- i18n: fa/en/ar updated for all new UI strings

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/Meezi.API/Controllers/HrController.cs

@@ -1,9 +1,12 @@
 using FluentValidation;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
 using Meezi.API.Models.Hr;
 using Meezi.API.Services;
 using Meezi.Core.Enums;
 using Meezi.Core.Interfaces;
+using Meezi.Core.Utilities;
+using Meezi.Infrastructure.Data;
 using Meezi.Shared;
 
 namespace Meezi.API.Controllers;
@@ -15,17 +18,20 @@ public class HrController : CafeApiControllerBase
     private readonly IValidator<CreateLeaveRequest> _leaveValidator;
     private readonly IValidator<ReviewLeaveRequest> _reviewValidator;
     private readonly IValidator<CreateSalaryRequest> _salaryValidator;
+    private readonly AppDbContext _db;
 
     public HrController(
         IHrService hr,
         IValidator<CreateLeaveRequest> leaveValidator,
         IValidator<ReviewLeaveRequest> reviewValidator,
-        IValidator<CreateSalaryRequest> salaryValidator)
+        IValidator<CreateSalaryRequest> salaryValidator,
+        AppDbContext db)
     {
         _hr = hr;
         _leaveValidator = leaveValidator;
         _reviewValidator = reviewValidator;
         _salaryValidator = salaryValidator;
+        _db = db;
     }
 
     [HttpGet("employees")]
@@ -201,4 +207,66 @@ public class HrController : CafeApiControllerBase
         if (data is null) return NotFoundError();
         return Ok(new ApiResponse<EmployeeSalaryDto>(true, data));
     }
+
+    /// <summary>Set or update username/password credentials for an employee. Owner/Manager only.</summary>
+    [HttpPut("employees/{employeeId}/credentials")]
+    public async Task<IActionResult> SetCredentials(
+        string cafeId,
+        string employeeId,
+        [FromBody] SetEmployeeCredentialsRequest request,
+        ITenantContext tenant,
+        CancellationToken ct)
+    {
+        if (EnsureCafeAccess(cafeId, tenant) is { } denied) return denied;
+        if (EnsureManager(tenant) is { } forbidden) return forbidden;
+
+        var username = request.Username.Trim().ToLowerInvariant();
+
+        if (string.IsNullOrWhiteSpace(username))
+            return BadRequest(new ApiResponse<object>(false, null, new ApiError("VALIDATION_ERROR", "Username is required.", "Username")));
+
+        if (request.Password.Length < 8)
+            return BadRequest(new ApiResponse<object>(false, null, new ApiError("VALIDATION_ERROR", "Password must be at least 8 characters.", "Password")));
+
+        var employee = await _db.Employees
+            .FirstOrDefaultAsync(e => e.Id == employeeId && e.CafeId == cafeId && e.DeletedAt == null, ct);
+
+        if (employee is null) return NotFoundError();
+
+        // Check username uniqueness within the cafe (excluding the employee itself)
+        var conflict = await _db.Employees
+            .AnyAsync(e => e.CafeId == cafeId && e.Id != employeeId && e.DeletedAt == null
+                        && e.Username != null && e.Username.ToLower() == username, ct);
+        if (conflict)
+            return Conflict(new ApiResponse<object>(false, null, new ApiError("USERNAME_TAKEN", "This username is already in use by another employee.")));
+
+        employee.Username = username;
+        employee.PasswordHash = PasswordHasher.Hash(request.Password);
+        await _db.SaveChangesAsync(ct);
+
+        return Ok(new ApiResponse<object>(true, null));
+    }
+
+    /// <summary>Remove username/password credentials from an employee. Owner/Manager only.</summary>
+    [HttpDelete("employees/{employeeId}/credentials")]
+    public async Task<IActionResult> RemoveCredentials(
+        string cafeId,
+        string employeeId,
+        ITenantContext tenant,
+        CancellationToken ct)
+    {
+        if (EnsureCafeAccess(cafeId, tenant) is { } denied) return denied;
+        if (EnsureManager(tenant) is { } forbidden) return forbidden;
+
+        var employee = await _db.Employees
+            .FirstOrDefaultAsync(e => e.Id == employeeId && e.CafeId == cafeId && e.DeletedAt == null, ct);
+
+        if (employee is null) return NotFoundError();
+
+        employee.Username = null;
+        employee.PasswordHash = null;
+        await _db.SaveChangesAsync(ct);
+
+        return Ok(new ApiResponse<object>(true, null));
+    }
 }