Replace dev/schema.sql with Laravel migrations in the backend

Baseline migration reproduces the production dump byte-for-byte (verified via
mariadb-dump diff); creates are hasTable-guarded so prod only records it.
Drop stock Laravel migrations that contradict prod and Sanctum's bundled one.

dev/dev

@@ -29,10 +29,10 @@ usage() {
 Usage: dev <command>
 
   setup                 composer install both apps + init local MariaDB
-  db start|stop|status  manage local MariaDB (data in .dev/mysql, port $DB_PORT); start applies dev/schema.sql
+  db start|stop|status  manage local MariaDB (data in .dev/mysql, port $DB_PORT); start runs backend migrations
   db shell              mysql client on the local DB
   db import <dump.sql>  drop + recreate the DB from a production dump (schema + data)
-  db reset              drop + recreate the DB with dev/schema.sql only (empty tables)
+  db reset              drop + recreate the DB, then migrate (empty tables)
   serve frontend        php artisan serve  -> http://127.0.0.1:$FRONTEND_PORT
   serve backend         php artisan serve  -> http://127.0.0.1:$BACKEND_PORT
   up                    db + both apps; Ctrl-C stops everything
@@ -64,6 +64,7 @@ db_start() {
     db_init
     if db_running; then
         echo "db: already running (pid $(cat "$MYSQL_PID"))"
+        db_migrate
         return
     fi
     # Ignore terminal Ctrl-C in the DB so `up` can shut it down cleanly after the app servers.
@@ -82,13 +83,14 @@ CREATE USER IF NOT EXISTS '$DB_USER'@'localhost' IDENTIFIED BY '$DB_PASS';
 GRANT ALL ON \`$DB_NAME\`.* TO '$DB_USER'@'127.0.0.1', '$DB_USER'@'localhost';
 FLUSH PRIVILEGES;
 SQL
-    db_apply_schema
+    db_migrate
     echo "db: listening on 127.0.0.1:$DB_PORT (pid $(cat "$MYSQL_PID"))"
 }
 
-# Idempotent (CREATE TABLE IF NOT EXISTS), so safe on every start; a no-op once tables exist.
-db_apply_schema() {
-    mariadb --socket="$MYSQL_SOCK" -uroot "$DB_NAME" <"$ROOT/dev/schema.sql"
+# The schema lives in think-backend/database/migrations; `migrate` is a no-op once applied.
+db_migrate() {
+    [ -f "$BACKEND/vendor/autoload.php" ] || composer_install
+    (cd "$BACKEND" && php artisan migrate --force --no-interaction)
 }
 
 db_recreate() {
@@ -124,8 +126,8 @@ db_import() {
 db_reset() {
     db_running || db_start
     db_recreate
-    db_apply_schema
-    echo "db: reset to dev/schema.sql"
+    db_migrate
+    echo "db: reset to empty schema"
 }
 
 composer_install() {