feat(core): professionalize state migration via Nix activation

- Move state migration logic from shell scripts to Home Manager activation
- Ensure migrations run automatically during rebuilds
- Delete obsolete bin/nomarchy-migrate and migrations/ directory

bin/nomarchy-dev-add-migration

@@ -1,14 +0,0 @@
-#!/bin/bash
-
-# Creates a new Nomarchy migration named after the unix timestamp of the last commit.
-# Only intended for Nomarchy developers.
-
-cd ~/.local/share/nomarchy
-migration_file="$HOME/.local/share/nomarchy/migrations/$(git log -1 --format=%cd --date=unix).sh"
-touch $migration_file
-
-if [[ $1 != "--no-edit" ]]; then
-  nvim $migration_file
-fi
-
-echo $migration_file

bin/nomarchy-migrate

@@ -1,29 +0,0 @@
-#!/bin/bash
-
-# Run all pending migrations to bring the system in line with the installed version.
-
-# Where we store an empty file for each migration that has already been performed.
-STATE_DIR="$HOME/.local/state/nomarchy/migrations"
-mkdir -p "$STATE_DIR"
-
-# Skipped migrations are tracked separately
-mkdir -p "$STATE_DIR/skipped"
-
-# Run any pending migrations
-for file in ~/.local/share/nomarchy/migrations/*.sh; do
-  filename=$(basename "$file")
-
-  if [[ ! -f $STATE_DIR/$filename && ! -f $STATE_DIR/skipped/$filename ]]; then
-    echo -e "\e[32m\nRunning migration (${filename%.sh})\e[0m"
-
-    if bash $file; then
-      touch "$STATE_DIR/$filename"
-    else
-      if gum confirm "Migration ${filename%.sh} failed. Skip and continue?"; then
-        touch "$STATE_DIR/skipped/$filename"
-      else
-        exit 1
-      fi
-    fi
-  fi
-done