Fix timeline editor duplicate events and drag-and-drop positioning

- Consolidated duplicate "Add Event" handlers by moving all JS from inline script to timeline-editor.js
- Fixed drag-and-drop position saving by correctly counting only event containers, not timeline header/rail elements
- Removed 1056 lines of duplicate inline JavaScript from edit.html.erb

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/controllers/timeline_events_controller.rb

@@ -150,7 +150,7 @@ class TimelineEventsController < ApplicationController
     
     render json: { 
       success: true, 
-      message: "Timeline event moved to position #{intended_position + 1}",
+      message: "New position saved", # "Timeline event moved to position #{intended_position + 1}"
       timeline_event: {
         id: timeline_event.id,
         position: timeline_event.position,