Display the saved creation timestamp (including time) across notes list, note view, and edit form. Adds a human-readable "Saved" line in application/views/notes/edit.php and application/views/notes/view.php, and updates application/views/notes/main.php to include the time using the format "M d, Y \a\t g:i A". The date input in the edit form still uses a YYYY-MM-DD value for the date picker, and entries with empty or zero dates show "N/A".
Introduces note categories with support for filtering, assigning, and managing categories. Adds category selection and creation to add/edit forms, category filtering to the notes list, and modals for deleting/merging categories and confirming note deletion. Updates controller and model logic to handle categories, and improves UI for notes management.
