ci: skip web npm ci + build:web-host on alpine runner (docker does it)

The forgejo-runner pod is alpine/musl. npm pulls native bindings for the
runner's detected libc, but lightningcss + @next/swc shipped variants
mismatch (gnu installed, musl missing or vice versa) — Next.js build
crashes with 'libc.musl-x86_64.so.1: cannot open shared object'.

docker/Dockerfile.sf-server already runs both `npm --prefix web ci` (line
32) and `npm run build:web-host` (line 48) inside node:26.1-slim (glibc),
so the runner copy is pure duplication anyway. Drop it. Image-build is the
single source of truth for the shipped web/ bundle.

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

.forgejo/workflows/self-deploy.yml

@@ -43,21 +43,23 @@ jobs:
       # which is on PATH for all steps. package.json declares
       # engines: { node: ">=26.1.0" } for runtime, but build-time tsc + tests
       # work on Node 22 — we just need to opt out of npm's engine enforcement.
-      - name: Install dependencies
+      # We intentionally skip the `web` npm ci + `build:web-host` here.
+      # docker/Dockerfile.sf-server re-runs both inside a glibc-based
+      # node:26.1-slim image (lines 32 + 48). The runner is alpine/musl
+      # and npm picks the wrong native bindings (lightningcss / @next/swc),
+      # so duplicating the work here just breaks. Image-build is the
+      # source of truth for what ships to prod.
+      - name: Install dependencies (core only)
         env:
           NPM_CONFIG_ENGINE_STRICT: "false"
         run: |
           set -eu
           echo "node $(node --version) / npm $(npm --version)"
           npm ci --engine-strict=false
-          npm --prefix web ci --engine-strict=false
 
       - name: Build core
         run: npm run build:core
 
-      - name: Build web host
-        run: npm run build:web-host
-
       - name: Typecheck extensions
         run: npm run typecheck:extensions