fix dockerfile: use bun instead of npm, add .dockerignore

Dockerfile

@@ -1,12 +1,12 @@
 # Stage 1: Build
-FROM node:20-alpine AS build
+FROM oven/bun:1 AS build
 WORKDIR /app
 COPY package.json bun.lock ./
-RUN npm install
+RUN bun install --frozen-lockfile
 COPY . .
 ARG VITE_NKODE_API_URL=https://api.nkode.donovankelly.xyz
 ENV VITE_NKODE_API_URL=$VITE_NKODE_API_URL
-RUN npm run build
+RUN bun run build
 
 # Stage 2: Serve
 FROM nginx:alpine