ci: add golangci, migration checks, and pre-commit

DEP-03: check-migrations-pair.sh; migrations/* в path filter; golangci-lint в CI; pre-commit; обновление engineering.mdc (TEST-04, enforcement).
Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/check-migrations-pair.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env sh
+# DEP-03: postgres and sqlite migration sets must have matching numbered pairs.
+set -eu
+
+ROOT="$(CDPATH= cd -- "$(dirname "$0")/.." && pwd)"
+PG="$ROOT/migrations/postgres"
+SQL="$ROOT/migrations/sqlite"
+
+list_nums() {
+  dir="$1"
+  ls "$dir" 2>/dev/null | sed -n 's/^\([0-9]\{6\}\)_.*\.up\.sql$/\1/p' | sort -u
+}
+
+pg_nums="$(list_nums "$PG")"
+sql_nums="$(list_nums "$SQL")"
+
+if [ "$pg_nums" != "$sql_nums" ]; then
+  echo "check-migrations-pair: postgres and sqlite migration numbers differ" >&2
+  echo "postgres only:" >&2
+  comm -23 <(printf '%s\n' "$pg_nums") <(printf '%s\n' "$sql_nums") >&2 || true
+  echo "sqlite only:" >&2
+  comm -13 <(printf '%s\n' "$pg_nums") <(printf '%s\n' "$sql_nums") >&2 || true
+  exit 1
+fi
+
+for n in $pg_nums; do
+  pg_up="$(ls "$PG"/${n}_*.up.sql 2>/dev/null | head -1)"
+  sql_up="$(ls "$SQL"/${n}_*.up.sql 2>/dev/null | head -1)"
+  if [ -z "$pg_up" ] || [ -z "$sql_up" ]; then
+    echo "check-migrations-pair: missing .up.sql for $n" >&2
+    exit 1
+  fi
+  pg_base="$(basename "$pg_up" .up.sql)"
+  sql_base="$(basename "$sql_up" .up.sql)"
+  if [ "$pg_base" != "$sql_base" ]; then
+    echo "check-migrations-pair: name mismatch for $n: $pg_base vs $sql_base" >&2
+    exit 1
+  fi
+done
+
+echo "check-migrations-pair: ok ($PG and $SQL)"