Integrate Bootstrap 5 and Bootstrap Icons into UI

- Add Bootstrap 5.3.3 + Icons via CDN to base.html
- Replace 315-line hand-written CSS with 35-line brand overrides
- Update all 13 templates with Bootstrap utility classes:
  - Responsive navbar with mobile hamburger menu
  - Consistent card-based layout for forms and profile
  - Proper button alignment with d-flex and d-grid utilities
  - List groups for data display (profile info)
  - Professional alerts and icons
- No backend changes, no build toolchain needed
- Responsive design works on mobile/tablet/desktop

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

web/templates/login.html

@@ -2,22 +2,31 @@
 {% block title %}Вход — EvoSync{% endblock %}
 
 {% block content %}
-<div class="form-card">
-    <h1>Вход</h1>
-    <form method="post" action="/login">
-        <div class="form-group">
-            <label for="email">Email</label>
-            <input type="email" id="email" name="email" value="{{ form.email if form else '' }}" required>
+<div class="row justify-content-center">
+    <div class="col-sm-10 col-md-6 col-lg-5">
+        <div class="card shadow-sm mt-4">
+            <div class="card-body p-4">
+                <h1 class="card-title h4 mb-4">Вход</h1>
+                <form method="post" action="/login">
+                    <div class="mb-3">
+                        <label for="email" class="form-label">Email</label>
+                        <input type="email" id="email" name="email" class="form-control"
+                               value="{{ form.email if form else '' }}" required>
+                    </div>
+                    <div class="mb-3">
+                        <label for="password" class="form-label">Пароль</label>
+                        <input type="password" id="password" name="password" class="form-control" required>
+                    </div>
+                    <div class="d-grid">
+                        <button type="submit" class="btn btn-primary">Войти</button>
+                    </div>
+                </form>
+                <div class="mt-3 text-center small">
+                    <a href="/forgot-password">Забыли пароль?</a><br>
+                    <a href="/register">Зарегистрироваться</a>
+                </div>
+            </div>
         </div>
-        <div class="form-group">
-            <label for="password">Пароль</label>
-            <input type="password" id="password" name="password" required>
-        </div>
-        <button type="submit" class="btn btn-primary">Войти</button>
-    </form>
-    <div class="form-links">
-        <a href="/forgot-password">Забыли пароль?</a><br>
-        <a href="/register">Зарегистрироваться</a>
     </div>
 </div>
 {% endblock %}