refactor: adopt portigo infrastructure patterns

Add config package with build-tag-switched dev/prod environments,
structured logging via zerolog, Taskfile for dev workflow, golangci-lint
config, testutil package, and improved DB setup with proper SQLite
pragmas and cleanup. Rename sqlc output package from gen to repository.

Switch to allowlist .gitignore, Alpine+UPX+scratch Dockerfile, and
CI pipeline with test/lint gates before deploy.

Dockerfile

@@ -1,4 +1,6 @@
-FROM golang:1.25.4-bookworm AS build
+FROM docker.io/golang:1.25.4-alpine AS build
+
+RUN apk add --no-cache upx
 
 WORKDIR /src
 COPY go.mod go.sum ./
@@ -6,24 +8,11 @@ RUN go mod download
 
 COPY . .
 RUN go tool gotailwind -i assets/css/input.css -o assets/css/output.css --minify
-RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o /c4 .
+RUN --mount=type=cache,target=/root/.cache/go-build \
+    CGO_ENABLED=0 go build -ldflags="-s" -o /bin/c4 .
+RUN upx -9 -k /bin/c4
 
-FROM debian:bookworm-slim
-
-RUN apt-get update && \
-    apt-get install -y --no-install-recommends ca-certificates wget && \
-    rm -rf /var/lib/apt/lists/*
-
-COPY --from=build /c4 /usr/local/bin/c4
-
-WORKDIR /app
-RUN mkdir data && chown games:games data
-
-USER games
-
-EXPOSE 8080
-
-HEALTHCHECK --interval=30s --timeout=5s --start-period=5s --retries=3 \
-    CMD wget -qO /dev/null http://localhost:8080/
-
-CMD ["c4"]
+FROM scratch
+ENV PORT=8080
+COPY --from=build /bin/c4 /
+ENTRYPOINT ["/c4"]