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>

.pre-commit-config.yaml

@@ -0,0 +1,19 @@
+# Local hooks (optional): install with `pre-commit install`
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v5.0.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+  - repo: https://github.com/dnephin/pre-commit-golang
+    rev: v0.5.1
+    hooks:
+      - id: go-fmt
+  - repo: local
+    hooks:
+      - id: prettier-web
+        name: prettier (web)
+        entry: bash -c 'cd web && npx prettier --check .'
+        language: system
+        files: ^web/
+        pass_filenames: false