Fix MySQL init script: executable bit + scope shell options in subshell

Without the exec bit the MySQL entrypoint sources the script instead of
executing it, leaking set -euo pipefail into MySQL's own startup shell and
aborting first-time initialization (container exits -> unhealthy -> compose
dependency failure).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

db/init/01-powerbi-user.sh

@@ -6,13 +6,17 @@
 # grants below take effect as soon as Alembic creates the reporting views.
 # For an already-initialized database, run scripts/powerbi_grants.sql instead
 # (see README → "Power BI").
-set -euo pipefail
+#
+# NOTE: this file must stay executable (git mode 100755). The MySQL image
+# *sources* non-executable init scripts into its own entrypoint shell, where
+# stray `set` options can break MySQL's startup. The subshell below keeps
+# everything scoped even if that happens.
+(
+  set -e
 
   if [ -z "${POWERBI_RO_PASSWORD:-}" ]; then
     echo "[init] POWERBI_RO_PASSWORD not set - skipping powerbi_ro user creation."
-  exit 0
-fi
-
+  else
     mysql -u root -p"${MYSQL_ROOT_PASSWORD}" <<SQL
 CREATE USER IF NOT EXISTS 'powerbi_ro'@'%' IDENTIFIED BY '${POWERBI_RO_PASSWORD}';
 GRANT SELECT ON \`${MYSQL_DATABASE}\`.\`vw_ncr_full\`          TO 'powerbi_ro'@'%';
@@ -20,5 +24,6 @@ GRANT SELECT ON \`${MYSQL_DATABASE}\`.\`vw_ncr_stage_history\` TO 'powerbi_ro'@'
 GRANT SELECT ON \`${MYSQL_DATABASE}\`.\`vw_ncr_costs\`         TO 'powerbi_ro'@'%';
 FLUSH PRIVILEGES;
 SQL
-
     echo "[init] powerbi_ro user created with SELECT on reporting views."
+  fi
+)