fix: resolve unbound variable error in deploy script migration check

The APPLIED_MIGRATIONS associative array triggered "unbound variable"
under set -u when empty (first run / seed-existing). Fix by initializing
with =() and using a safe helper function with ${:-} default syntax.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/deploy-prod.sh

@@ -248,12 +248,19 @@ CREATE TABLE IF NOT EXISTS shared.schema_migrations (
 SQL
 ok "Migration tracking table ready"
 
+# Helper: check if a migration has been applied (safe with set -u)
+is_applied() {
+  local key="$1"
+  # Use a subshell test to avoid unbound variable with set -u on empty associative arrays
+  [[ -n "${APPLIED_MIGRATIONS[$key]:-}" ]]
+}
+
 # Step 5b: Get list of already-applied migrations
-declare -A APPLIED_MIGRATIONS
+declare -A APPLIED_MIGRATIONS=()
 while IFS= read -r fname; do
   fname=$(echo "$fname" | xargs)  # trim whitespace
   [ -n "$fname" ] && APPLIED_MIGRATIONS["$fname"]=1
-done < <(run_sql -t -c "SELECT filename FROM shared.schema_migrations ORDER BY filename;")
+done < <(run_sql -t -c "SELECT filename FROM shared.schema_migrations ORDER BY filename;" 2>/dev/null || true)
 
 APPLIED_COUNT=${#APPLIED_MIGRATIONS[@]}
 log "Previously applied migrations: $APPLIED_COUNT"
@@ -304,7 +311,7 @@ PENDING_COUNT=0
 APPLIED_THIS_RUN=0
 
 for filename in "${MIGRATION_FILES[@]}"; do
-  if [ -n "${APPLIED_MIGRATIONS[$filename]+x}" ]; then
+  if is_applied "$filename"; then
     continue
   fi
   ((PENDING_COUNT++))
@@ -317,7 +324,7 @@ else
   echo ""
 
   for filename in "${MIGRATION_FILES[@]}"; do
-    if [ -n "${APPLIED_MIGRATIONS[$filename]+x}" ]; then
+    if is_applied "$filename"; then
       continue
     fi