docs: update npm commands to bun in README and documentation files

- Replace npm install with bun install
- Replace npm start/test/build with bun equivalents
- Update deployment and testing documentation
- Maintain consistency with project's bun-first approach

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

IMPLEMENTATION_COMPLETE.md

@@ -327,9 +327,9 @@ All requested features have been **fully implemented** across the Adopt-a-Street
 - `__tests__/routes/` - auth, streets, tasks, posts, events, rewards, reports tests
 
 **Test Scripts:**
-- `npm test` - Run all tests
-- `npm run test:coverage` - With coverage report
-- `npm run test:watch` - Watch mode for TDD
+- `bun test` - Run all tests
+- `bun run test:coverage` - With coverage report
+- `bun run test:watch` - Watch mode for TDD
 
 #### Frontend Testing
 
@@ -348,8 +348,8 @@ All requested features have been **fully implemented** across the Adopt-a-Street
 - `__tests__/auth-flow.integration.test.js` - Full auth flow test
 
 **Test Scripts:**
-- `npm test` - Run in watch mode
-- `npm run test:coverage` - With coverage report
+- `bun test` - Run in watch mode
+- `bun run test:coverage` - With coverage report
 
 #### Documentation
 
@@ -440,20 +440,20 @@ All requested features have been **fully implemented** across the Adopt-a-Street
 #### Backend
 ```bash
 cd backend
-npm install
+bun install
 # Create .env with: MONGO_URI, JWT_SECRET, CLOUDINARY_* variables
 npm start          # Start server on port 5000
-npm test           # Run tests
-npm run test:coverage  # Run tests with coverage
+bun test           # Run tests
+bun run test:coverage  # Run tests with coverage
 ```
 
 #### Frontend
 ```bash
 cd frontend
-npm install
-npm start          # Start dev server on port 3000
-npm test           # Run tests
-npm run build      # Production build
+bun install
+bun start          # Start dev server on port 3000
+bun test           # Run tests
+bun run build      # Production build
 ```
 
 ---
@@ -537,7 +537,7 @@ RUN npm ci
 COPY . .
 
 # Build production bundle
-RUN npm run build
+RUN bun run build
 
 # --- Production stage with nginx ---
 FROM nginx:alpine