fix(ci): allow Dockerfile build to fetch internal gitea modules

mcp-chassis (added in commit 658f4ba) is hosted at gitea.d-ma.be, and
Gitea returns http:// in its go-import meta tag. Default go module
resolution goes through proxy.golang.org (which can't reach internal
hosts) and falls back to direct git, which gets the http:// URL and
refuses it.

Fix:
- GOPRIVATE=gitea.d-ma.be — skip proxy.golang.org
- GOPROXY=direct — direct git, no proxy attempt
- GOSUMDB=off — bypass sumdb (also doesn't know internal modules)
- git config insteadOf rewrites http:// → https:// for gitea.d-ma.be

Without this, gitea-mcp CI Build & Import failed on the chassis port
(sha=658f4ba). Re-running CI should now succeed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -1,5 +1,16 @@
 FROM golang:1.26-alpine AS build
 WORKDIR /src
+
+# Fetch internal gitea-hosted Go modules (e.g. mcp-chassis) without going
+# through proxy.golang.org and without HTTP→HTTPS surprises. Gitea returns
+# http:// in its go-import meta tag, so rewrite to https here and bypass
+# the module proxy + sumdb.
+RUN apk add --no-cache git && \
+    git config --global url."https://gitea.d-ma.be/".insteadOf "http://gitea.d-ma.be/"
+ENV GOPRIVATE=gitea.d-ma.be
+ENV GOPROXY=direct
+ENV GOSUMDB=off
+
 COPY go.mod go.sum ./
 RUN go mod download
 COPY . .