Add structured logging, navigation bar, and code cleanup

## Backend
- Add Pino logging framework with timestamps and structured output
- Replace all console.error statements (49+) with proper logging levels
- Fix Drizzle ORM bug: replace invalid .get() calls with .limit(1)
- Remove unused auth routes file (already in index.js)
- Make internal functions private (remove unnecessary exports)
- Simplify code by removing excessive debug logging

## Frontend
- Add navigation bar to layout with:
  - User's callsign display
  - Navigation links (Dashboard, QSOs, Settings)
  - Logout button with red color distinction
- Navigation only shows when user is logged in
- Dark themed design matching footer

## Documentation
- Update README.md with new project structure
- Update docs/DOCUMENTATION.md with logging and nav bar info
- Add logger.js to configuration section

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/backend/config/logger.js

@@ -0,0 +1,20 @@
+import pino from 'pino';
+
+const isDevelopment = process.env.NODE_ENV !== 'production';
+
+export const logger = pino({
+  level: process.env.LOG_LEVEL || (isDevelopment ? 'debug' : 'info'),
+  transport: isDevelopment
+    ? {
+        target: 'pino-pretty',
+        options: {
+          colorize: true,
+          translateTime: 'SYS:standard',
+          ignore: 'pid,hostname',
+        },
+      }
+    : undefined,
+  timestamp: pino.stdTimeFunctions.isoTime,
+});
+
+export default logger;