Drop Dockerfile.ci, which nothing has built since 2025

It was added in 941e5f0 (2024-09-21) as a cache-less variant, because
the BuildKit cache mounts in the main Dockerfile were causing trouble in
CI, and the workflow pointed at it with `file: Dockerfile.ci`. That line
was removed in 6719538 (2025-02-27, "Switch to using native ARM64
builders"), which returned the build to the default Dockerfile - but the
file itself stayed behind.

Nothing has referenced it since. It had meanwhile drifted from the real
Dockerfile (no RELEASE_BUILD argument, no cache mounts) while Renovate
kept bumping its base image pin, so every one of those bumps was a pull
request for a file that is never built.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -80,7 +80,7 @@ jobs:
           fi
 
           git fetch --no-tags origin main
-          if git diff --name-only origin/main HEAD -- Dockerfile Dockerfile.ci | grep -q .; then
+          if git diff --name-only origin/main HEAD -- Dockerfile | grep -q .; then
             echo 'A Dockerfile changed; the image will be built.'
             echo 'build=true' >> "$GITHUB_OUTPUT"
           else

Dockerfile.ci

@@ -1,35 +0,0 @@
-#######################################
-#                                     #
-# Stage 1: building                   #
-#                                     #
-#######################################
-
-FROM docker.io/rust:1.98.0-slim-trixie AS build
-
-RUN apt-get update && apt-get install -y build-essential pkg-config libssl-dev libsqlite3-dev
-
-WORKDIR /app
-
-COPY . /app
-
-RUN cargo build --release
-
-#######################################
-#                                     #
-# Stage 2: packaging                  #
-#                                     #
-#######################################
-
-FROM docker.io/debian:trixie-slim
-
-RUN apt-get update && apt-get install -y ca-certificates sqlite3 && \
-    apt-get clean && \
-    rm -rf /var/lib/apt/lists/*
-
-WORKDIR /app
-
-COPY --from=build /app/target/release/baibot .
-
-ENTRYPOINT ["/bin/sh", "-c"]
-
-CMD ["/app/baibot"]

renovate.json

@@ -25,7 +25,7 @@
 			"platformAutomerge": false
 		},
 		{
-			"description": "The release image's base (Dockerfile and Dockerfile.ci). Gated by ci.yml's docker-build job, which builds the image exactly as Publish does but with `push: false`, and which only runs when a Dockerfile actually changed.",
+			"description": "The release image's base (Dockerfile). Gated by ci.yml's docker-build job, which builds the image exactly as Publish does but with `push: false`, and which only runs when the Dockerfile actually changed.",
 			"matchManagers": [
 				"dockerfile"
 			],