fix(editor): true top-align via CodeField expands + move refresh

Two changes Stefan flagged on 0.1.3:

(1) Short files were still vertically centered. The previous
fix (CrossAxisAlignment.stretch on the Row) only stretched
the SingleChildScrollView viewport — the CodeField inside
still had its natural content-sized height and sat centered
in the larger viewport. Drop the SCV wrapper entirely and
set `expands: true` (with `minLines: null` + `maxLines:
null`, the underlying TextField's required combination) on
the CodeField. The widget now fills its parent's bounded
height, the line-number gutter runs the full editor height,
and line 1 sits at the literal top edge. Standard IDE
behaviour.

(2) The round outlined Refresh button sandwiched between
New (filled-tonal) and Save (filled-tonal) in the editor
toolbar was a visual-style outlier — Stefan called it
"dazwischen, sieht falsch aus". Refresh is also
semantically scoped to the file list, not the open
editor, so move it out of the editor toolbar entirely and
into a small FLOWS header bar at the top of the file-list
panel. The editor toolbar now reads:
  [Back] file.yaml ● [Spacer] [New] [Save] [Run]
— four filled-tonal/filled buttons, no style outliers.
The file-list panel reads:
  ┌───────────────────────┐
  │ FLOWS              ⟲  │
  ├───────────────────────┤
  │ flow-a                │
  │ flow-b                │
  └───────────────────────┘

Adds `listHeader` to FlowEditorStrings (de + en both
"FLOWS" — same word, all-caps).

Version 0.1.3 -> 0.1.4.

Signed-off-by: flemming-it <sf@flemming.it>

pubspec.yaml

@@ -1,6 +1,6 @@
 name: fai_studio_flow_editor
 description: Swappable inline YAML editor for F∆I Studio flows.
-version: 0.1.3
+version: 0.1.4
 publish_to: 'none'
 repository: https://git.flemming.ai/fai/studio-flow-editor