🔧(backend) fix Pylint configurations

Removing the __init__.py makes it impossible for Pylint to get the sources
to lint from the root folder. We manually set all the paths pylint will lint.

That's not a big deal, as we'll remove Pylint any soon to rely only on ruff.
I took inspiration from marsha or magnify project.

I removed the now useless bash script to run Pylint command. It saves us
wrapper! Plus, having a lint command running with different option locally
and in the CI was quite a pain.

Locally linter was running on diff files; Fixed! CI and make command has now
the same behavior.

bin/pylint

@@ -1,38 +0,0 @@
-#!/usr/bin/env bash
-
-# shellcheck source=bin/_config.sh
-source "$(dirname "${BASH_SOURCE[0]}")/_config.sh"
-
-declare diff_from
-declare -a paths
-declare -a args
-
-# Parse options
-for arg in "$@"
-do
-    case $arg in
-        --diff-only=*)
-            diff_from="${arg#*=}"
-            shift
-            ;;
-        -*)
-            args+=("$arg")
-            shift
-            ;;
-        *)
-            paths+=("$arg")
-            shift
-            ;;
-    esac
-done
-
-if [[ -n "${diff_from}" ]]; then
-    # Run pylint only on modified files located in src/backend
-    # (excluding deleted files and migration files)
-    # shellcheck disable=SC2207
-    paths=($(git diff "${diff_from}" --name-only --diff-filter=d -- src/backend ':!**/migrations/*.py' | grep -E '^src/backend/.*\.py$'))
-fi
-
-# Fix docker vs local path when project sources are mounted as a volume
-read -ra paths <<< "$(echo "${paths[@]}" | sed "s|src/backend/||g")"
-_dc_run app-dev pylint "${paths[@]}" "${args[@]}"