chore(deps): consolidate and bump all dependencies (#838)

* chore(deps): bump all dependencies and migrate to eslint flat config

Consolidates all pending dependency update PRs into a single update.
Bumps dependencies to latest compatible versions, migrates from
deprecated .eslintrc.js to eslint.config.mjs flat config, and fixes
lint issues surfaced by updated rules. Bumps package version to 4.0.7.

Key dependency updates:
- eslint 8→9 (flat config)
- typescript-eslint 7→8
- c8 10→11
- concurrently 8→9
- eslint-config-prettier 9→10
- eslint-plugin-promise 6→7
- sinon 18→19
- typescript 5.0→5.9
- prettier 3.0→3.8
- ethers 6.9→6.16
- hardhat 2.22→2.28

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

* chore: modernize husky pre-commit hook and lint-staged config

Remove deprecated husky.sh sourcing (v10 compat) and remove
unnecessary `git add` from lint-staged (auto-staged in modern versions).

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: ryanio

.eslintignore

@@ -1,4 +1 @@
-#!/bin/sh
-. "$(dirname "$0")/_/husky.sh"
-
 npx lint-staged

.eslintrc.js

@@ -0,0 +1,46 @@
+import eslint from "@eslint/js";
+import tseslint from "typescript-eslint";
+import prettierConfig from "eslint-config-prettier";
+import prettierPlugin from "eslint-plugin-prettier";
+import importPlugin from "eslint-plugin-import";
+
+export default tseslint.config(
+  {
+    ignores: [
+      "lib/**",
+      "src/artifacts/**",
+      "src/typechain-types/**",
+      "cache/**",
+      "coverage/**",
+      "eslint.config.mjs",
+    ],
+  },
+  eslint.configs.recommended,
+  ...tseslint.configs.recommended,
+  prettierConfig,
+  {
+    plugins: {
+      prettier: prettierPlugin,
+      import: importPlugin,
+    },
+    languageOptions: {
+      parserOptions: {
+        project: ["tsconfig.json"],
+      },
+    },
+    rules: {
+      "prettier/prettier": "error",
+      "no-unused-expressions": "off",
+      "no-unused-vars": "off",
+      "@typescript-eslint/no-unused-expressions": "off",
+      "@typescript-eslint/no-unused-vars": [
+        "error",
+        { argsIgnorePattern: "^_", varsIgnorePattern: "^_" },
+      ],
+      "@typescript-eslint/no-require-imports": "off",
+      "@typescript-eslint/no-explicit-any": "off",
+      "@typescript-eslint/require-await": "error",
+      "object-shorthand": ["error", "always"],
+    },
+  },
+);