fix: make SSH config directive matching case-insensitive

resolve_ssh_alias() used a case statement that only matched
'HostName' (capital N), but OpenSSH treats config directives
as case-insensitive: 'Hostname', 'HostName', 'HOSTNAME' and
'hostname' are all equivalent. A config like

    Host retailpos-hites-qa
        Hostname 10.60.16.35
        User retailpos
        IdentityFile ~/.ssh/retailpos-key

produced 'has no HostName' even though one was present.

Enable 'shopt -s nocasematch' around the parsing loop so the
case branches match any casing. nocasematch was chosen over
${var,,} because the latter requires bash 4+, and macOS still
ships bash 3.2.57 as /bin/bash.

The 'Host' pattern itself remains case-sensitive, matching
ssh's own behavior.

Verified against: tabbed/spaced/mixed indentation, lowercase,
uppercase, mixed-casing directives, the user's exact config,
and the previous regression cases.

scripts/build-and-push.sh

@@ -134,6 +134,9 @@ resolve_ssh_alias() {
   local -a patterns
   # Force whitespace-aware splitting (the script's global IFS excludes spaces).
   local IFS=$' \t\n'
+  # SSH config directives are case-insensitive (HostName == Hostname == HOSTNAME).
+  # nocasematch is supported in bash 3.2 (unlike ${var,,} which needs 4+).
+  shopt -s nocasematch
   while read -r line || [[ -n "$line" ]]; do
     # First whitespace-separated token (tabs and spaces collapse uniformly).
     read -r first _ <<< "$line"
@@ -163,6 +166,7 @@ resolve_ssh_alias() {
       esac
     fi
   done < "$config"
+  shopt -u nocasematch
 
   (( in_block )) \
     || die "No matching Host entry in $config for alias '$alias'. Use user@host[:port] or check ~/.ssh/config."