fix: update Go version in Dockerfile from 1.22 to 1.26

[larinkonstantin]

Fixes #37

PROBLEM
Building the Docker image fails because go.mod requires Go 1.26, but the Dockerfile uses golang:1.22-alpine:

 => [build 3/4] COPY . .                                                                                                                                                                                                             0.1s
 => ERROR [build 4/4] RUN go build -o RealiTLScanner .                                                                                                                                                                                    0.2s
------
 > [build 4/4] RUN go build -o RealiTLScanner .:
0.137 go: go.mod requires go >= 1.26 (running go 1.22.12; GOTOOLCHAIN=local)
------
Dockerfile:4
--------------------
   2 |     WORKDIR /src
   3 |     COPY . .
   4 | >>> RUN go build -o RealiTLScanner .
   5 |
   6 |     FROM alpine:latest
--------------------
ERROR: failed to build: failed to solve: process "/bin/sh -c go build -o RealiTLScanner ." did not complete successfully: exit code: 1

FIX
Update the base image in Dockerfile to match the version required by go.mod