refactor: fix biome linting issues and update project documentation

- Fix 36+ biome linting issues reducing errors/warnings from 227 to 191
- Replace explicit 'any' types with proper TypeScript interfaces
- Fix React hooks dependencies and useCallback patterns
- Resolve unused variables and parameter assignment issues
- Improve accessibility with proper label associations
- Add comprehensive API documentation for admin and security features
- Update README.md with accurate PostgreSQL setup and current tech stack
- Create complete documentation for audit logging, CSP monitoring, and batch processing
- Fix outdated project information and missing developer workflows

lib/nonce-utils.ts

@@ -0,0 +1,28 @@
+import { headers } from "next/headers";
+
+/**
+ * Get the CSP nonce from request headers (server-side only)
+ */
+export async function getNonce(): Promise<string | undefined> {
+  try {
+    const headersList = await headers();
+    return headersList.get("X-Nonce") || undefined;
+  } catch {
+    // Headers not available (e.g., in client-side code)
+    return undefined;
+  }
+}
+
+/**
+ * Create script props with nonce for CSP compliance
+ */
+export function createScriptProps(nonce?: string) {
+  return nonce ? { nonce } : {};
+}
+
+/**
+ * Create style props with nonce for CSP compliance
+ */
+export function createStyleProps(nonce?: string) {
+  return nonce ? { nonce } : {};
+}