ios: get TestFlight CI signing working

Replace the old testflight-release workflow with a single
`testflight.yml` Gitea Actions workflow and rework the fastlane `beta`
lane: match-based app-store signing into a disposable CI keychain,
XcodeGen project generation, version/build-number bumping, and upload
to TestFlight. Pin Ruby to 3.1.7 for the runner.

Squashes the iterative CI signing debugging history into one commit.

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

.gitea/workflows/testflight.yml

@@ -0,0 +1,70 @@
+name: TestFlight
+
+on:
+  workflow_dispatch:
+  push:
+    tags:
+      - "v*"
+
+jobs:
+  testflight:
+    runs-on: xcode
+    defaults:
+      run:
+        shell: bash
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: "3.1.7"
+          bundler-cache: true
+          working-directory: ios
+
+      - name: Install XcodeGen
+        run: |
+          set -euo pipefail
+          if ! command -v xcodegen >/dev/null 2>&1; then
+            brew install xcodegen
+          fi
+
+      - name: Prepare Runner Keychain
+        env:
+          HOME: /var/lib/act_runner
+        run: |
+          set -euo pipefail
+          mkdir -p "${HOME}/Library/Keychains"
+
+          login_keychain="${HOME}/Library/Keychains/login.keychain"
+          if [ ! -f "${login_keychain}-db" ]; then
+            security create-keychain -p "" "${login_keychain}"
+          fi
+
+          security unlock-keychain -p "" "${login_keychain}" 2>/dev/null || \
+            security unlock-keychain -p "sybil-ci-keychain-password" "${login_keychain}" 2>/dev/null || true
+          security default-keychain -d user -s "${login_keychain}"
+          security list-keychains -d user -s "${login_keychain}-db"
+          security delete-keychain "${HOME}/Library/Keychains/sybil_ci_keychain" >/dev/null 2>&1 || true
+          rm -f "${HOME}/Library/Keychains/sybil_ci_keychain" "${HOME}/Library/Keychains/sybil_ci_keychain-db"
+
+      - name: Upload to TestFlight
+        working-directory: ios
+        env:
+          HOME: /var/lib/act_runner
+          APP_STORE_CONNECT_KEY_ID: ${{ secrets.APP_STORE_CONNECT_KEY_ID }}
+          APP_STORE_CONNECT_ISSUER_ID: ${{ secrets.APP_STORE_CONNECT_ISSUER_ID }}
+          APP_STORE_CONNECT_KEY_CONTENT: ${{ secrets.APP_STORE_CONNECT_KEY_CONTENT }}
+          MATCH_PASSWORD: ${{ secrets.MATCH_PASSWORD }}
+          MATCH_GIT_URL: ${{ secrets.MATCH_GIT_URL }}
+          MATCH_GIT_BASIC_AUTHORIZATION: ${{ secrets.MATCH_GIT_BASIC_AUTHORIZATION }}
+          FASTLANE_SKIP_UPDATE_CHECK: "1"
+          FASTLANE_XCODEBUILD_SETTINGS_TIMEOUT: "120"
+        run: |
+          export PATH="/Users/runner/hostedtoolcache/Ruby/3.1.7/arm64/bin:${PATH}"
+          ruby --version
+          bundle exec fastlane ios beta