feat: redesign sidebar with corporate branding and ProsApp logo

- Logo: network image in white card + tagline
- Sidebar: deep navy gradient (#0D1B3E) with blue accent active states
- MenuItem: left accent bar indicator, cleaner hover, better contrast
- Mode toggle: gradient button matching brand colors
- TextSeparator: uppercase label with divider line

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/ui/shared/widgets/logo.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-import 'package:google_fonts/google_fonts.dart';
 
 class Logo extends StatelessWidget {
   const Logo({super.key});
@@ -7,21 +6,38 @@ class Logo extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return Container(
-      padding: EdgeInsets.only(top: 30),
-      child: Row(
-        mainAxisAlignment: MainAxisAlignment.center,
+      padding: const EdgeInsets.symmetric(vertical: 28, horizontal: 20),
+      child: Column(
         children: [
-          Image.asset('logo.png', width: 50, height: 50),
-          SizedBox(width: 8),
-          Text(
-            'Prosapp',
-            style: GoogleFonts.montserratAlternates(
-              fontSize: 20,
-              fontWeight: FontWeight.w200,
+          Container(
+            padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 10),
+            decoration: BoxDecoration(
               color: Colors.white,
+              borderRadius: BorderRadius.circular(12),
+            ),
+            child: Image.network(
+              'https://www.prosapp.co/img/logo_prosapp.png',
+              height: 32,
+              fit: BoxFit.contain,
+              errorBuilder: (_, __, ___) => const Text(
+                'ProsApp',
+                style: TextStyle(
+                  fontSize: 16,
+                  fontWeight: FontWeight.bold,
+                  color: Color(0xFF42A4EF),
+                ),
+              ),
+            ),
+          ),
+          const SizedBox(height: 8),
+          const Text(
+            'Conecta con profesionales',
+            style: TextStyle(
+              color: Color(0xFF8BAFD4),
+              fontSize: 10,
+              letterSpacing: 0.3,
             ),
           ),
-          SizedBox(width: 10),
         ],
       ),
     );