fix: transform README to end-user focused and correct configuration

Major updates:
- Changed title to emphasize Jira project connectivity
- Added "What You Can Do" section with natural language examples
- Added "Perfect For" section targeting specific user roles
- Simplified Quick Start to 2-minute setup guide
- Added comprehensive Real-World Examples section with emojis
- FIXED incorrect ATLASSIAN_JIRA_URL reference to correct ATLASSIAN_SITE_NAME
- Created user-friendly Troubleshooting section with common issues
- Added detailed FAQ addressing user concerns about permissions, security, and compatibility
- Removed technical transport modes and CLI command documentation
- Added Support section for getting help
- Updated .env.example with descriptive comments and API token generation link
- Documented alternative config keys support (jira, atlassian-jira, etc.)
- Verified all configuration against actual source code implementation

Author: aashari

.env.example

@@ -1,7 +1,10 @@
 # Enable debug logging
 DEBUG=false
 
-# Atlassian Configuration
+# Atlassian Configuration (required for Jira access)
+# Your Jira site name (for https://your-instance.atlassian.net)
 ATLASSIAN_SITE_NAME=your-instance
-ATLASSIAN_USER_EMAIL=your-email@example.com
+# Your Atlassian account email
+ATLASSIAN_USER_EMAIL=your-email@example.com  
+# Your Atlassian API token (generate at https://id.atlassian.com/manage-profile/security/api-tokens)
 ATLASSIAN_API_TOKEN=