Add event colors (Catppuccin Mocha) and read-only week view for users

Admins can now pick a color per event from a Catppuccin Mocha palette;
existing events default to blue. Colors flow through to both the admin
timeline and the new "Неделя" tab in the user view, which reuses the
admin's weekly grid in a read-only mode. Also reworks event blocks to
show a single-line "start–end title" so short events no longer overflow,
tidies the admin toolbar, and expands mobile responsiveness across both
frontends.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/utils.py

@@ -102,7 +102,8 @@ async def materialize_events(
             title=event.title,
             start_time=event.start_time,
             duration_min=event.duration_min,
-            repeat_weekly=False
+            repeat_weekly=False,
+            color=event.color or "blue"
         ))
 
     result = await db.execute(select(Event).where(Event.repeat_weekly == True))
@@ -146,7 +147,8 @@ async def materialize_events(
                     title=exception.replacement_title or event.title,
                     start_time=exception.replacement_start_time or event.start_time,
                     duration_min=exception.replacement_duration_min or event.duration_min,
-                    repeat_weekly=True
+                    repeat_weekly=True,
+                    color=exception.replacement_color or event.color or "blue"
                 ))
                 continue
 
@@ -158,7 +160,8 @@ async def materialize_events(
                 title=event.title,
                 start_time=event.start_time,
                 duration_min=event.duration_min,
-                repeat_weekly=True
+                repeat_weekly=True,
+                color=event.color or "blue"
             ))
 
         current_date += timedelta(days=1)