ci: reduce workflows to fork-relevant CI, fix upstream checkouts (Issue #2)

Removed ~37 workflow files that are unmodified upstream tooling this fork
doesn't use (Netlify, SonarCloud, Localazy, release-drafter/backport,
GitHub issue-triage bots, npm-publish, Cloudflare Pages deploy, Docker
push to ghcr.io/element-hq). Enabling Actions for this repo would have
activated all of them simultaneously against a single-capacity shared
runner - most would just fail loudly and starve the one job slot shared
with other repos.

Kept build-and-test.yaml (the actual comprehensive build+test+desktop
workflow) and its build_desktop_*.yaml sub-workflows. Fixed: push trigger
now targets `main` (was `staging`/`master`, neither of which exist here -
push events never fired at all before), 4 checkout steps now check out
this fork instead of element-hq/element-web, and removed the macOS
desktop build job since the registered runner (builder-1) has no macOS
label and would queue forever instead of failing cleanly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.github/workflows/build-and-test.yaml

@@ -16,8 +16,7 @@ on:
     merge_group:
         types: [checks_requested]
     push:
-        # We do not build on push to develop as the merge_group check handles that
-        branches: [staging, master]
+        branches: [main]
 
     # support triggering from other workflows
     workflow_call:
@@ -60,7 +59,7 @@ jobs:
             - name: Checkout code
               uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
               with:
-                  repository: element-hq/element-web
+                  repository: ${{ github.repository }}
                   persist-credentials: false
 
             - uses: pnpm/action-setup@fc06bc1257f339d1d5d8b3a19a8cae5388b55320 # v5
@@ -137,7 +136,7 @@ jobs:
             - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
               with:
                   persist-credentials: false
-                  repository: element-hq/element-web
+                  repository: ${{ github.repository }}
 
             - name: 📥 Download artifact
               uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8
@@ -237,15 +236,8 @@ jobs:
             arch: ${{ matrix.arch }}
             blob_report: true
 
-    build_ed_macos:
-        needs: prepare_ed
-        name: "Desktop macOS"
-        uses: ./.github/workflows/build_desktop_macos.yaml
-        # Skip macOS builds on PRs, as the Linux amd64 build is enough of a smoke test and includes the screenshot tests
-        # and we have a very low limit of concurrent macos runners (5) across the Github org.
-        if: github.event_name != 'pull_request' || contains(github.event.pull_request.labels.*.name, 'X-Run-All-Tests')
-        with:
-            blob_report: true
+    # build_ed_macos entfernt: der einzige Gitea-Actions-Runner (builder-1, CFGMON) hat
+    # kein macOS-Label - der Job wuerde nie einen Runner finden statt sauber zu scheitern.
 
     complete:
         name: end-to-end-tests
@@ -256,7 +248,6 @@ jobs:
             - prepare_ed
             - build_ed_windows
             - build_ed_linux
-            - build_ed_macos
         if: always()
         runs-on: ubuntu-24.04
         steps:
@@ -264,7 +255,7 @@ jobs:
               if: needs.build_ew.outputs.skip == 'false'
               with:
                   persist-credentials: false
-                  repository: element-hq/element-web
+                  repository: ${{ github.repository }}
 
             - uses: pnpm/action-setup@fc06bc1257f339d1d5d8b3a19a8cae5388b55320 # v5
               if: needs.build_ew.outputs.skip == 'false'