feat: rename to gitea-mcp-extended and add package publishing workflows

Rename the fork from gitea-mcp to gitea-mcp-extended to reflect the
significantly expanded tool coverage (299 vs upstream's 93 tools).

- Rename Go module path and all import references
- Rename binary to gitea-mcp-extended in Makefile, Dockerfile, .gitignore
- Point .goreleaser.yaml gitea_urls to git.lethalbits.com
- Replace release-tag workflow with goreleaser + Generic Package Registry publishing
- Replace release-nightly workflow with cross-platform build + nightly package publishing
- Update CLAUDE.md project description and tool count

Dockerfile

@@ -17,16 +17,16 @@ COPY . .
 RUN --mount=type=cache,target=/go/pkg/mod \
     --mount=type=cache,target=/root/.cache/go-build \
     CGO_ENABLED=0 GOOS=${TARGETOS:-linux} GOARCH=${TARGETARCH:-amd64} \
-    go build -trimpath -ldflags="-s -w -X main.Version=${VERSION}" -o gitea-mcp
+    go build -trimpath -ldflags="-s -w -X main.Version=${VERSION}" -o gitea-mcp-extended
 
 # Final stage
 FROM gcr.io/distroless/static-debian12:nonroot
 
 WORKDIR /app
-COPY --from=builder --chown=nonroot:nonroot /app/gitea-mcp .
+COPY --from=builder --chown=nonroot:nonroot /app/gitea-mcp-extended .
 
 USER nonroot:nonroot
 
 LABEL org.opencontainers.image.version="${VERSION}"
 
-CMD ["/app/gitea-mcp"]
+CMD ["/app/gitea-mcp-extended"]