feat: Sistema de Usuarios - Backend CRUD + JWT Auth (Issue #1)

Implementación fundacional del proyecto PruebaGentle:
- Arquitectura Clean/Hexagonal: Core, Infrastructure, API
- 6 Stored Procedures para CRUD + autenticación
- JWT authentication con BCrypt password hashing
- Docker Compose (SQL Server + Backend)
- Solución .NET 10 con Dapper + SqlClient

Closes #1

Backend/Sql/CreateUsersTable.sql

@@ -0,0 +1,8 @@
+CREATE TABLE Users (
+    Id INT IDENTITY(1,1) PRIMARY KEY,
+    Username NVARCHAR(50) NOT NULL UNIQUE,
+    PasswordHash NVARCHAR(255) NOT NULL,
+    Email NVARCHAR(100) NOT NULL UNIQUE,
+    NombreCompleto NVARCHAR(100) NOT NULL,
+    FechaCreacion DATETIME NOT NULL DEFAULT GETDATE()
+);

Backend/Sql/sp_User_Create.sql

@@ -0,0 +1,13 @@
+CREATE OR ALTER PROCEDURE sp_User_Create
+    @Username NVARCHAR(50),
+    @PasswordHash NVARCHAR(255),
+    @Email NVARCHAR(100),
+    @NombreCompleto NVARCHAR(100)
+AS
+BEGIN
+    SET NOCOUNT ON;
+
+    INSERT INTO Users (Username, PasswordHash, Email, NombreCompleto)
+    OUTPUT INSERTED.Id, INSERTED.Username, INSERTED.Email, INSERTED.NombreCompleto, INSERTED.FechaCreacion
+    VALUES (@Username, @PasswordHash, @Email, @NombreCompleto);
+END

Backend/Sql/sp_User_Delete.sql

@@ -0,0 +1,9 @@
+CREATE OR ALTER PROCEDURE sp_User_Delete
+    @Id INT
+AS
+BEGIN
+    SET NOCOUNT ON;
+
+    DELETE FROM Users
+    WHERE Id = @Id;
+END

Backend/Sql/sp_User_GetAll.sql

@@ -0,0 +1,9 @@
+CREATE OR ALTER PROCEDURE sp_User_GetAll
+AS
+BEGIN
+    SET NOCOUNT ON;
+
+    SELECT Id, Username, Email, NombreCompleto, FechaCreacion
+    FROM Users
+    ORDER BY FechaCreacion DESC;
+END

Backend/Sql/sp_User_GetById.sql

@@ -0,0 +1,10 @@
+CREATE OR ALTER PROCEDURE sp_User_GetById
+    @Id INT
+AS
+BEGIN
+    SET NOCOUNT ON;
+
+    SELECT Id, Username, Email, NombreCompleto, FechaCreacion
+    FROM Users
+    WHERE Id = @Id;
+END

Backend/Sql/sp_User_GetByUsername.sql

@@ -0,0 +1,10 @@
+CREATE OR ALTER PROCEDURE sp_User_GetByUsername
+    @Username NVARCHAR(50)
+AS
+BEGIN
+    SET NOCOUNT ON;
+
+    SELECT Id, Username, PasswordHash, Email, NombreCompleto, FechaCreacion
+    FROM Users
+    WHERE Username = @Username;
+END

Backend/Sql/sp_User_Update.sql

@@ -0,0 +1,16 @@
+CREATE OR ALTER PROCEDURE sp_User_Update
+    @Id INT,
+    @Username NVARCHAR(50),
+    @Email NVARCHAR(100),
+    @NombreCompleto NVARCHAR(100)
+AS
+BEGIN
+    SET NOCOUNT ON;
+
+    UPDATE Users
+    SET Username = @Username,
+        Email = @Email,
+        NombreCompleto = @NombreCompleto
+    OUTPUT INSERTED.Id, INSERTED.Username, INSERTED.Email, INSERTED.NombreCompleto, INSERTED.FechaCreacion
+    WHERE Id = @Id;
+END