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

pkg/gitea/gitea.go

@@ -7,8 +7,8 @@ import (
 	"net/http"
 
 	"code.gitea.io/sdk/gitea"
-	mcpContext "git.lethalbits.com/lethalbits/gitea-mcp/pkg/context"
-	"git.lethalbits.com/lethalbits/gitea-mcp/pkg/flag"
+	mcpContext "git.lethalbits.com/lethalbits/gitea-mcp-extended/pkg/context"
+	"git.lethalbits.com/lethalbits/gitea-mcp-extended/pkg/flag"
 )
 
 func NewClient(token string) (*gitea.Client, error) {