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>

frontend/Dockerfile

@@ -1,5 +1,5 @@
 # Multi-stage build for ARM compatibility (Raspberry Pi)
-FROM node:18-alpine AS builder
+FROM oven/bun:1-alpine AS builder
 
 WORKDIR /app
 
@@ -7,13 +7,13 @@ WORKDIR /app
 COPY package*.json ./
 
 # Install dependencies
-RUN npm ci
+RUN bun install --frozen-lockfile
 
 # Copy source code
 COPY . .
 
 # Build production bundle
-RUN npm run build
+RUN bun run build
 
 # --- Production stage with nginx ---
 FROM nginx:alpine