chore(housekeeping): canonical git.d-ma.be host + honest version string

- Dockerfile: GOPRIVATE and the http→https insteadOf rewrite now name
  git.d-ma.be (was the pre-rename gitea.d-ma.be; masked at build time only by
  GOPROXY=direct + GOSUMDB=off).
- .context/PROJECT.md Repo URL → git.d-ma.be, adapters regenerated
  (CLAUDE.md, AGENTS.md, .cursorrules, .aider.conventions.md, system-prompt.txt).
- main.go: version is now a `-ldflags -X main.version` overridable var defaulting
  to "dev" instead of a hardcoded, drifting "0.1.0".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -1,13 +1,13 @@
 FROM golang:1.26-alpine AS build
 WORKDIR /src
 
-# Fetch internal gitea-hosted Go modules (e.g. mcp-chassis) without going
+# Fetch internal git-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
+    git config --global url."https://git.d-ma.be/".insteadOf "http://git.d-ma.be/"
+ENV GOPRIVATE=git.d-ma.be
 ENV GOPROXY=direct
 ENV GOSUMDB=off