fix(docker-setup): yaml_get handles 4-space YAML indentation

Hub YAML is generated by Go's yaml.v3 which uses 4-space indentation.
The yaml_get helper was matching "  key:" (2 spaces) so all extractions
silently returned empty — BASE_DOMAIN stayed as homeserver.local and
CF_TUNNEL_TOKEN was never set from hub config.

Strip leading whitespace before key matching, making yaml_get
indentation-agnostic.

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

scripts/docker-setup.sh

@@ -1473,10 +1473,15 @@ EOF
 #-------------------------------------------------------------------------------
 yaml_get() {
     local file="$1" section="$2" key="$3"
-    awk -v s="${section}:" -v k="  ${key}:" '
+    awk -v s="${section}:" -v k="${key}:" '
         /^[[:alpha:]]/ { in_s = ($0 == s) }
-        in_s && index($0, k) == 1 {
-            sub(/^[^:]*: */, ""); gsub(/^"|"$/, ""); print; exit
+        in_s && /^[[:space:]]/ {
+            line = $0; sub(/^[[:space:]]+/, "", line)
+            if (index(line, k) == 1) {
+                sub(/^[^:]*:[[:space:]]*/, "", line)
+                gsub(/^"|"$/, "", line)
+                print line; exit
+            }
         }
     ' "$file"
 }