Polish Pattern Template UI: dialog sizing, KC editor layout, and conventions

- Fix dialog/canvas sizing: fit-content dialog follows canvas width, canvas
  max-width: 100% prevents overflow, horizontal resize supported
- Move pattern template dropdown above FPS/mode/smoothing in KC editor
- Remove emoji from pattern template dropdown options and auto-generated names
- Remove placeholder option from pattern template select, default to first
- Rename default pattern template from "Default" to "Full Screen"
- Add UI conventions to CLAUDE.md (hint pattern, select dropdown rules)

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

server/src/wled_controller/static/locales/en.json

@@ -396,5 +396,9 @@
   "pattern.capture_bg": "Capture Background",
   "pattern.source_for_bg": "Source for Background:",
   "pattern.source_for_bg.none": "-- Select source --",
-  "pattern.delete_selected": "Delete Selected"
+  "pattern.delete_selected": "Delete Selected",
+  "pattern.name.hint": "A descriptive name for this rectangle layout",
+  "pattern.description.hint": "Optional notes about where or how this pattern is used",
+  "pattern.visual_editor.hint": "Click + buttons to add rectangles. Drag edges to resize, drag inside to move.",
+  "pattern.rectangles.hint": "Fine-tune rectangle positions and sizes with exact coordinates (0.0 to 1.0)"
 }