feat: Add postbuild cleanup and web-ext lint validation

- Add scripts/postbuild-cleanup.cjs to remove unsafe Function patterns
- Add lint:extension script for web-ext validation
- Fix manifest_firefox.json strict_min_version to 112.0
- Reduces web-ext warnings from 14 to 10

scripts/postbuild-cleanup.cjs

@@ -0,0 +1,51 @@
+#!/usr/bin/env node
+// Post-build cleanup script to remove unsafe patterns flagged by web-ext lint
+// This runs after webpack build to sanitize the output
+
+const fs = require('fs');
+const path = require('path');
+
+const BUILD_DIR = path.join(__dirname, '../packages/extension/build');
+
+const replacements = [
+  // Replace Function("return this")() with globalThis
+  {
+    search: /Function\s*\(\s*["']return this["']\s*\)\s*\(\s*\)/g,
+    replace: 'globalThis'
+  },
+  // Replace Function("return this") (without call) with a function returning globalThis
+  {
+    search: /Function\s*\(\s*["']return this["']\s*\)/g,
+    replace: '(function(){return globalThis})'
+  }
+];
+
+const jsFiles = fs.readdirSync(BUILD_DIR).filter(f => f.endsWith('.js'));
+
+let totalReplacements = 0;
+
+jsFiles.forEach(file => {
+  const filePath = path.join(BUILD_DIR, file);
+  let content = fs.readFileSync(filePath, 'utf8');
+  let fileReplacements = 0;
+
+  replacements.forEach(({ search, replace }) => {
+    const matches = content.match(search);
+    if (matches) {
+      fileReplacements += matches.length;
+      content = content.replace(search, replace);
+    }
+  });
+
+  if (fileReplacements > 0) {
+    fs.writeFileSync(filePath, content);
+    console.log(`  ${file}: ${fileReplacements} replacement(s)`);
+    totalReplacements += fileReplacements;
+  }
+});
+
+if (totalReplacements > 0) {
+  console.log(`\n✓ Cleaned ${totalReplacements} unsafe Function patterns`);
+} else {
+  console.log('✓ No unsafe Function patterns found');
+}