cleanup: .cutter-info + .timeline-container .shown modifiers — 4 inline display references gone

Both the cutter-info bar (resolution/duration/fps/selection readouts) and the timeline-container (timeline + start/end inputs) were hidden by default via inline style="display:none;" in HTML, then loadCutterFromPath() set .style.display = 'flex' / 'block' once a video was loaded.

Moved both into CSS with the same pattern as 4.6.126 (.queue-details.expanded) and 4.6.132 (.clip-template-wrap.shown):
- Base .cutter-info / .timeline-container rule sets display:none
- .shown modifier flips to flex / block respectively (preserves the original visible-state layout)
- HTML drops the inline style attribute
- JS uses classList.add('shown') instead of poking at .style.display

Four inline-style references gone (2 HTML + 2 TS), no behavior change.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/index.html

@@ -334,7 +334,7 @@
                             </div>
                         </div>
 
-                        <div class="cutter-info" id="cutterInfo" style="display:none">
+                        <div class="cutter-info" id="cutterInfo">
                             <div class="cutter-info-item">
                                 <span class="cutter-info-label" id="cutterInfoDurationLabel">Dauer</span>
                                 <span class="cutter-info-value" id="infoDuration">--:--:--</span>
@@ -353,7 +353,7 @@
                             </div>
                         </div>
 
-                        <div class="timeline-container" id="timelineContainer" style="display:none">
+                        <div class="timeline-container" id="timelineContainer">
                             <div class="timeline" id="timeline" onclick="seekTimeline(event)">
                                 <div class="timeline-selection" id="timelineSelection"></div>
                                 <div class="timeline-current" id="timelineCurrent"></div>