fix(build): add post-build script to fix HTML paths for Chrome extension

- Create scripts/fix-build-paths.js to convert absolute paths to relative
- Update build script to run fix-build-paths.js after plasmo build
- Add build:raw script for raw plasmo build without fix

Problem: Plasmo generates HTML with absolute paths (href="/file.css")
which causes ERR_FILE_NOT_FOUND in Chrome extensions.

Solution: Post-build script replaces /path with ./path

surfsense_browser_extension/scripts/fix-build-paths.js

@@ -0,0 +1,63 @@
+#!/usr/bin/env node
+/**
+ * Post-build script to fix absolute paths in Plasmo-generated HTML files.
+ * 
+ * Problem: Plasmo generates HTML files with absolute paths (e.g., href="/file.css")
+ * which don't work in Chrome extensions (ERR_FILE_NOT_FOUND).
+ * 
+ * Solution: Replace absolute paths with relative paths (e.g., href="./file.css")
+ */
+
+const fs = require('fs');
+const path = require('path');
+
+const BUILD_DIR = path.join(__dirname, '..', 'build', 'chrome-mv3-prod');
+const HTML_FILES = ['popup.html', 'sidepanel.html'];
+
+function fixPaths(filePath) {
+    if (!fs.existsSync(filePath)) {
+        console.log(`⚠️  File not found: ${filePath}`);
+        return false;
+    }
+
+    let content = fs.readFileSync(filePath, 'utf8');
+    const originalContent = content;
+
+    // Replace absolute paths with relative paths
+    // href="/something" -> href="./something"
+    // src="/something" -> src="./something"
+    content = content.replace(/href="\/([^"]+)"/g, 'href="./$1"');
+    content = content.replace(/src="\/([^"]+)"/g, 'src="./$1"');
+
+    if (content !== originalContent) {
+        fs.writeFileSync(filePath, content, 'utf8');
+        console.log(`✅ Fixed paths in: ${path.basename(filePath)}`);
+        return true;
+    } else {
+        console.log(`ℹ️  No changes needed: ${path.basename(filePath)}`);
+        return false;
+    }
+}
+
+function main() {
+    console.log('🔧 Fixing build paths for Chrome extension...\n');
+
+    if (!fs.existsSync(BUILD_DIR)) {
+        console.error(`❌ Build directory not found: ${BUILD_DIR}`);
+        console.error('   Run "pnpm build" first.');
+        process.exit(1);
+    }
+
+    let fixedCount = 0;
+    for (const htmlFile of HTML_FILES) {
+        const filePath = path.join(BUILD_DIR, htmlFile);
+        if (fixPaths(filePath)) {
+            fixedCount++;
+        }
+    }
+
+    console.log(`\n✨ Done! Fixed ${fixedCount} file(s).`);
+}
+
+main();
+