Add spacing, a larger body, and photo uploads to the coach news form

The post-composer screen was cramped and text-only, and its "audience"
picker exposed the same "which team(s)" choice the create-event screen
already dropped -- hard-lock teams to the coach's active team instead
(hidden field, required=True so a tampered empty submission can't
silently become club-wide), matching how CoachCreateEventView.teams
already works. Photos reuse management's own NewsPhotoUploadForm/
NewsPhoto machinery, first upload becomes the main picture.

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

static/css/app.css

@@ -3948,6 +3948,9 @@
   .h-24 {
     height: calc(var(--spacing) * 24);
   }
+  .h-40 {
+    height: calc(var(--spacing) * 40);
+  }
   .h-44 {
     height: calc(var(--spacing) * 44);
   }
@@ -4311,6 +4314,9 @@
   .resize {
     resize: both;
   }
+  .resize-y {
+    resize: vertical;
+  }
   .scrollbar-gutter-stable {
     scrollbar-gutter: stable;
   }