Refactor: Extract CSS and dichotomous key into external files

[nate-layman]

Current State

The app.R file currently contains:

1. Inline CSS styles embedded in the R code
2. The dichotomous key decision tree hardcoded as an R list structure

Proposed Changes

Extract CSS to external stylesheet

• Move CSS from inline styles in app.R to a dedicated www/styles.css file
• Benefits:
  • Cleaner separation of concerns
  • Easier to maintain and modify styles
  • Better syntax highlighting and linting for CSS
  • Follows standard Shiny app structure

Extract dichotomous key to external data file

• Move the decision tree structure from app.R into a separate file (e.g., dichotra_decision_tree.json or similar)
• Benefits:
  • Easier to update the decision tree logic without touching R code
  • Could potentially make it user-editable or configurable
  • Cleaner app.R structure
  • Makes the decision tree more visible and maintainable

Files Affected

• /app/app.R - remove inline CSS and decision tree
• /app/www/styles.css - new file for styles
• /app/dichotra_decision_tree.json (or .yaml/.R) - new file for decision tree logic

Priority

Low - nice-to-have refactoring for maintainability