refactor: use REPO_NAMES in preflight.sh

- Replace REPO_1/2/3_NAME in required vars with REPO_NAMES
- Update GitHub repos existence check to iterate REPO_NAMES
- Update runner repos validation to check against REPO_NAMES words

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

preflight.sh

@@ -171,14 +171,15 @@ check_runners_ini_format() {
       errors=$((errors + 1))
     fi
 
-    # repos: must be "all" or a known REPO_*_NAME
+    # repos: must be "all" or a name from REPO_NAMES
     if [[ "$repos" != "all" ]] && [[ -n "$repos" ]]; then
       local repos_valid=false
-      for var in REPO_1_NAME REPO_2_NAME REPO_3_NAME; do
-        if [[ "$repos" == "${!var:-}" ]]; then repos_valid=true; break; fi
+      local _rn
+      for _rn in ${REPO_NAMES:-}; do
+        if [[ "$repos" == "$_rn" ]]; then repos_valid=true; break; fi
       done
       if ! $repos_valid; then
-        log_error "  → [$section] repos='$repos' (must be 'all' or a known repo name)"
+        log_error "  → [$section] repos='$repos' (must be 'all' or a name from REPO_NAMES)"
         errors=$((errors + 1))
       fi
     fi
@@ -244,7 +245,7 @@ REQUIRED_VARS=(
   GITEA_DOMAIN GITEA_INTERNAL_URL
   GITEA_BACKUP_INTERNAL_URL BACKUP_STORAGE_PATH
   GITHUB_USERNAME GITHUB_TOKEN
-  REPO_1_NAME REPO_2_NAME REPO_3_NAME
+  REPO_NAMES
   RUNNER_DEFAULT_IMAGE RUNNER_DEFAULT_DATA_PATH LOCAL_RUNNER_DATA_PATH
   NGINX_CONTAINER_NAME NGINX_CONF_PATH SSL_MODE
 )
@@ -496,13 +497,8 @@ check_github_repos() {
     return 1
   fi
 
-  for var in REPO_1_NAME REPO_2_NAME REPO_3_NAME; do
-    local repo="${!var:-}"
-    if [[ -z "$repo" ]]; then
-      log_error "  → ${var} is empty"
-      all_ok=1
-      continue
-    fi
+  local repo
+  for repo in ${REPO_NAMES:-}; do
     if ! curl -sf -H "Authorization: token ${GITHUB_TOKEN:-}" "https://api.github.com/repos/${GITHUB_USERNAME}/${repo}" -o /dev/null 2>/dev/null; then
       log_error "  → GitHub repo ${repo} not found under ${GITHUB_USERNAME}"
       all_ok=1