feat: comprehensive Biome linting fixes and code quality improvements

Major code quality overhaul addressing 58% of all linting issues:

• Type Safety Improvements:
  - Replace all any types with proper TypeScript interfaces
  - Fix Map component shadowing (renamed to CountryMap)
  - Add comprehensive custom error classes system
  - Enhance API route type safety

• Accessibility Enhancements:
  - Add explicit button types to all interactive elements
  - Implement useId() hooks for form element accessibility
  - Add SVG title attributes for screen readers
  - Fix static element interactions with keyboard handlers

• React Best Practices:
  - Resolve exhaustive dependencies warnings with useCallback
  - Extract nested component definitions to top level
  - Fix array index keys with proper unique identifiers
  - Improve component organization and prop typing

• Code Organization:
  - Automatic import organization and type import optimization
  - Fix unused function parameters and variables
  - Enhanced error handling with structured error responses
  - Improve component reusability and maintainability

Results: 248 → 104 total issues (58% reduction)
- Fixed all critical type safety and security issues
- Enhanced accessibility compliance significantly
- Improved code maintainability and performance

lib/csvFetcher.ts

@@ -1,7 +1,8 @@
 // Simplified CSV fetcher - fetches and parses CSV data without any processing
 // Maps directly to SessionImport table fields
-import fetch from "node-fetch";
+
 import { parse } from "csv-parse/sync";
+import fetch from "node-fetch";
 
 // Raw CSV data interface matching SessionImport schema
 interface RawSessionImport {
@@ -38,7 +39,7 @@ export async function fetchAndParseCsv(
 ): Promise<RawSessionImport[]> {
   const authHeader =
     username && password
-      ? "Basic " + Buffer.from(`${username}:${password}`).toString("base64")
+      ? `Basic ${Buffer.from(`${username}:${password}`).toString("base64")}`
       : undefined;
 
   const res = await fetch(url, {