Manual per-calendar color choice for calendar mode

Each linked person can pin one of the panel's four non-black/white
colors (Yellow/Red/Blue/Green) to their own calendar instead of relying
on calendar_render.py's old auto-cycle-by-owner-name order -- owner-only,
like adding a calendar in the first place. Colors resolve against
whichever palette a frame actually renders with (including a custom
Advanced configuration override), so a pinned "Blue" stays this frame's
actual blue. Event color bars/dots are also bigger and rounded now
across agenda/week/month views, easier to tell apart at a glance.

server/app/templates/frame_calendar.html

@@ -60,13 +60,26 @@
             <li>
               <p class="calendar-user-name">{{ u.display_name }}{% if u.is_self %} (you){% endif %}</p>
               {% if u.calendars %}
+                {% set current_palette = frame.palette_rgb or default_palette_rgb %}
+                {% set current_hex = palette_to_hex(current_palette) %}
                 {% for c in u.calendars %}
-                  <label class="checkbox-row" style="margin-top: 6px;">
+                  <div class="checkbox-row calendar-row" style="margin-top: 6px;">
                     <input type="checkbox" class="calendar-toggle"
                            data-user-id="{{ u.user_id }}" data-key="{{ c.key }}" data-label="{{ c.label }}"
                            {% if c.included %}checked{% endif %}>
-                    {{ c.label }}
-                  </label>
+                    <label style="margin: 0; font-weight: normal;">{{ c.label }}</label>
+                    {% if u.is_self %}
+                      <span class="calendar-color-picker" data-key="{{ c.key }}">
+                        {% for idx in range(2, 6) %}
+                          <button type="button" class="color-swatch {% if c.color_index == idx %}selected{% endif %}"
+                                  data-index="{{ idx }}" title="{{ calendar_color_labels[idx] }}"
+                                  style="background-color: {{ current_hex[idx] }};"></button>
+                        {% endfor %}
+                        <button type="button" class="color-swatch color-swatch-auto {% if c.color_index is none %}selected{% endif %}"
+                                data-index="" title="Auto (assigned automatically)">Auto</button>
+                      </span>
+                    {% endif %}
+                  </div>
                 {% endfor %}
               {% elif u.is_self %}
                 <p class="sub" style="margin-top: 6px;">No calendars set up yet -- add an ICS link or CalDAV account in <a href="/settings">Settings</a>.</p>