ci: drop build-server-self.yml — it builds a deleted Dockerfile

a6a933d ("kms is the Go service on /v1/kms — delete the Infisical console")
removed Dockerfile.server and Dockerfile.web but left .github/workflows/
untouched. build-server-self.yml still passes `file: Dockerfile.server`, so
every run since fails immediately:

  ERROR: failed to solve: failed to read dockerfile:
         open Dockerfile.server: no such file or directory

Delete the workflow rather than repoint it. It existed to build a second,
"self-contained" variant of the same server into ghcr.io/luxfi/kms:server —
a duplicate path for one job. The main Dockerfile (Build KMS) already builds
the server, and the :server image is consumed by nothing: zero pods reference
it on either lux-k8s or hanzo-k8s, and the only remaining mentions are this
workflow and a historical note in hanzo/kms/DEPRECATED.md.

Leaves one Dockerfile and one server build.

Co-authored-by: Hanzo Dev <dev@hanzo.ai>

.github/workflows/build-server-self.yml

@@ -1,53 +0,0 @@
-name: Build KMS Server (self-contained)
-
-# Self-contained workflow — does NOT call hanzoai/.github reusable workflow.
-# Runs directly on the amd64 ARC pool to bypass the cross-org `secrets:
-# inherit` initialization failure that's blocking the standard pipeline.
-
-on:
-  push:
-    branches: [main]
-    paths:
-      - 'cmd/**'
-      - 'pkg/**'
-      - 'go.mod'
-      - 'go.sum'
-      - 'Dockerfile.server'
-      - '.github/workflows/build-server-self.yml'
-  workflow_dispatch:
-
-permissions:
-  contents: read
-  packages: write
-
-jobs:
-  build:
-    runs-on: lux-build-amd64
-    timeout-minutes: 30
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Login to GHCR
-        uses: docker/login-action@v3
-        with:
-          registry: ghcr.io
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-
-      - name: Set up Buildx
-        uses: docker/setup-buildx-action@v3
-
-      - name: Build and push (linux/amd64, headless server)
-        uses: docker/build-push-action@v6
-        with:
-          context: .
-          file: Dockerfile.server
-          platforms: linux/amd64
-          build-args: |
-            GITHUB_TOKEN=${{ secrets.GITHUB_TOKEN }}
-          push: true
-          tags: |
-            ghcr.io/luxfi/kms:server
-            ghcr.io/luxfi/kms:server-${{ github.sha }}
-          cache-from: type=gha
-          cache-to: type=gha,mode=max