Migrate Breweries to a vertical slice (Features.Breweries)

Moves brewery CRUD from the Service.Breweries/Infrastructure.Repository
layered split into a single Features.Breweries project: MediatR
commands/queries replace BreweryService, and the repository moves in
alongside its own controller. Extracts Infrastructure.Sql out of
Infrastructure.Repository (just the generic ADO.NET connection/base-repo
plumbing) since Breweries no longer needs the rest of that project, while
Auth and UserAccount repos still do until their own migration.

Also fixes the API.Core and Infrastructure.Repository.Tests Dockerfiles,
which were restoring against COPY destinations that didn't match the
projects' actual relative paths (silently working only because of the
COPY . . that followed); both now restore against Core.slnx with correctly
nested paths, verified with a real docker build.

web/backend/Infrastructure/Infrastructure.Sql/DefaultSqlConnectionFactory.cs

@@ -0,0 +1,69 @@
+using System.Data.Common;
+using Microsoft.Data.SqlClient;
+using Microsoft.Extensions.Configuration;
+
+namespace Infrastructure.Sql;
+
+/// <summary>
+/// Default <see cref="ISqlConnectionFactory"/> implementation that creates SQL Server connections,
+/// resolving the connection string from environment variables or application configuration.
+/// </summary>
+/// <param name="configuration">The application configuration, used as a fallback source for the connection string.</param>
+public class DefaultSqlConnectionFactory(IConfiguration configuration)
+    : ISqlConnectionFactory
+{
+    private readonly string _connectionString = GetConnectionString(
+        configuration
+    );
+
+    /// <summary>
+    /// Resolves the SQL Server connection string, preferring (in order): the <c>DB_CONNECTION_STRING</c>
+    /// environment variable, a connection string built from individual <c>DB_*</c> environment variables
+    /// via <see cref="SqlConnectionStringHelper.BuildConnectionString"/>, and finally the <c>"Default"</c>
+    /// connection string from <paramref name="configuration"/>.
+    /// </summary>
+    /// <param name="configuration">The application configuration to fall back to.</param>
+    /// <returns>The resolved SQL Server connection string.</returns>
+    /// <exception cref="InvalidOperationException">
+    /// Thrown when no connection string can be resolved from any of the supported sources.
+    /// </exception>
+    private static string GetConnectionString(IConfiguration configuration)
+    {
+        // Check for full connection string first
+        var fullConnectionString = Environment.GetEnvironmentVariable(
+            "DB_CONNECTION_STRING"
+        );
+        if (!string.IsNullOrEmpty(fullConnectionString))
+        {
+            return fullConnectionString;
+        }
+
+        // Try to build from individual environment variables (preferred method for Docker)
+        try
+        {
+            return SqlConnectionStringHelper.BuildConnectionString();
+        }
+        catch (InvalidOperationException)
+        {
+            // Fall back to configuration-based connection string if env vars are not set
+            var connString = configuration.GetConnectionString("Default");
+            if (!string.IsNullOrEmpty(connString))
+            {
+                return connString;
+            }
+
+            throw new InvalidOperationException(
+                "Database connection string not configured. Set DB_CONNECTION_STRING or DB_SERVER, DB_NAME, DB_USER, DB_PASSWORD env vars or ConnectionStrings:Default."
+            );
+        }
+    }
+
+    /// <summary>
+    /// Creates a new, unopened <see cref="SqlConnection"/> using the resolved connection string.
+    /// </summary>
+    /// <returns>A new <see cref="SqlConnection"/> instance.</returns>
+    public DbConnection CreateConnection()
+    {
+        return new SqlConnection(_connectionString);
+    }
+}