build(docker): standardize Dockerfile and .dockerignore

Add --frozen-lockfile to bun install, pin base image tags,
add missing EXPOSE directives, and standardize .dockerignore entries.

Author: coopbri

.dockerignore

@@ -0,0 +1,13 @@
+node_modules
+.git
+.env*
+!.env.production
+!.env.local.template
+dist
+build
+.output
+target
+*.log
+.turbo
+coverage
+.nyc_output

Dockerfile

@@ -6,7 +6,7 @@ WORKDIR /app
 # Build
 FROM base AS builder
 COPY package.json bun.lock* ./
-RUN bun install
+RUN bun install --frozen-lockfile
 COPY . .
 RUN bun run build