fix(docker): bump base image from alpine3.16 to alpine3.20

node:20-alpine3.16 is a frozen tag — Alpine 3.16 went EOL in May 2024
and Docker Hub stopped publishing newer Node 20 builds against it,
locking the runtime at Node 20.2.0 (May 2023).

The stale Node ABI and old musl 1.2.3 are the most likely cause of the
recurring SIGSEGV (exitCode=139) crashes seen on civitai-dp-prod SSR
pods — ~50/day across all SSR-eligible nodes. The Prisma 6.13 native
musl engine was published ~14 months after this Node build, exactly
the skew that produces native segfaults on edge cases like a Postgres
connection closing mid-query (the chronic "Error { kind: Closed }"
pattern in our logs).

alpine3.20 ships current Node 20.18+, current openssl 3.0.13, and
musl 1.2.5. Same major Node, same package manager, same build steps —
no application changes required.

Dockerfile

@@ -1,6 +1,6 @@
 ##### DEPENDENCIES
 
-FROM node:20-alpine3.16 AS deps
+FROM node:20-alpine3.20 AS deps
 RUN apk add --no-cache libc6-compat
 WORKDIR /app
 
@@ -23,7 +23,7 @@ RUN --mount=type=cache,id=pnpm-store,target=/root/.local/share/pnpm/store \
 
 ##### BUILDER
 
-FROM node:20-alpine3.16 AS builder
+FROM node:20-alpine3.20 AS builder
 ARG NEXT_PUBLIC_IMAGE_LOCATION
 ARG NEXT_PUBLIC_CONTENT_DECTECTION_LOCATION
 ARG NEXT_PUBLIC_MAINTENANCE_MODE
@@ -44,7 +44,7 @@ RUN --mount=type=cache,target=/app/.next/cache \
 
 ##### RUNNER
 
-FROM node:20-alpine3.16 AS runner
+FROM node:20-alpine3.20 AS runner
 WORKDIR /app
 
 ENV NODE_ENV=production