feat: change to dark mode theme

based on dracula midnight colors

memory-bank/activeContext.md

@@ -16,6 +16,7 @@
 - Setting up the Vite/TypeScript/Tailwind environment.
 
 ## Active Decisions
+- **Dark Mode Implementation**: Adopted a Dracula Midnight theme (`#21222c` background) as the primary interface style. Added custom Dracula color palette to `tailwind.config.js`.
 - Using **Vite** for the build tool.
 - Using **Vanilla TypeScript** to avoid framework overhead.
 - Using **Vitest** for unit testing calculation logic.

memory-bank/progress.md

@@ -1,18 +1,19 @@
 # Progress Tracking
 
 ## Milestones
-- [ ] Initial Environment & Docs Setup
-- [ ] Core Calculation Engine
-- [ ] Web UI & Integration
-- [ ] Final Build & Polish
+- [x] Initial Environment & Docs Setup
+- [x] Core Calculation Engine
+- [x] Web UI & Integration
+- [x] Final Build & Polish
+- [x] Firebase deployment
 
 ## Todo List
 - [x] Create project structure
 - [x] Initialize Memory Bank documents
-- [ ] Create Blueprint documents (PRD, Architecture)
-- [ ] Project setup (Vite, TS, Tailwind, Vitest)
-- [ ] Implement `src/calculator.ts`
-- [ ] Write tests in `src/calculator.test.ts`
-- [ ] Implement `index.html` UI
-- [ ] Implement `src/main.ts` glue code
-- [ ] Verify build output
+- [x] Create Blueprint documents (PRD, Architecture)
+- [x] Project setup (Vite, TS, Tailwind, Vitest)
+- [x] Implement `src/calculator.ts`
+- [x] Write tests in `src/calculator.test.ts`
+- [x] Implement `index.html` UI
+- [x] Implement `src/main.ts` glue code
+- [x] Verify build output