refactor(repo): conform structure to AGENTS.md (web->frontend, internal/api->cmd/webui/{api,handlers}, docs/README+CHANGELOGs, module .gitignores, drop stray library/ and committed debug bins)

backend/Dockerfile.prod

@@ -3,7 +3,7 @@ WORKDIR /src
 COPY backend/go.mod backend/go.sum ./
 RUN go mod download
 COPY backend/ ./
-RUN CGO_ENABLED=0 go build -trimpath -o /server ./cmd/server
+RUN CGO_ENABLED=0 go build -trimpath -o /server ./cmd/webui
 
 FROM alpine:3.20 AS runner
 RUN adduser -D -H app