fix: correct dependencies and add Dockerfile

- Mark direct dependencies properly in go.mod (fsnotify, fpdf, goldmark)
- Remove duplicate Theme assignment in type_webserver.go
- Add Dockerfile for multi-stage build (was missing from repo)
- Update PLAN.md with completed tasks

Co-Authored-By: Claude (glm-5) <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,40 @@
+# Build stage
+FROM golang:1.22-alpine AS builder
+
+WORKDIR /app
+
+# Copy go.mod and go.sum first for caching
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Build the binary with static linking
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -ldflags '-extldflags "-static" -X main.APP_VERSION=${APP_VERSION:-latest} -X main.COMMIT_ID=${COMMIT_ID:-undefined}' -o gocv .
+
+# Runtime stage
+FROM alpine:latest
+
+RUN apk --no-cache add ca-certificates tzdata
+
+WORKDIR /app
+
+# Copy the binary from builder
+COPY --from=builder /app/gocv .
+
+# Copy config file
+COPY config.yaml .
+
+# Create directories for content and output
+RUN mkdir -p /app/content /app/output /app/themes
+
+# Copy themes
+COPY --from=builder /app/themes ./themes
+
+# Expose default port
+EXPOSE 80
+
+# Default command runs serve mode
+ENTRYPOINT ["./gocv"]
+CMD ["serve"]