This commit introduces two major features:
1. Project Custom Fields: Add custom_fields JSON column to projects table (migration 085), support for flexible custom data storage, display and edit in project views
2. File Attachments System: Add project_attachments and client_attachments tables (migration 086), new ProjectAttachment and ClientAttachment models, full CRUD operations, file upload/download/delete, client-visible attachments support
Additional improvements: Enhanced data tables, updated project/client/invoice/timer views, improved UI for attachments and custom fields management
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