Scene URL Enhancements

Three small fixes for the URLs field on a scene's Edit tab:

1. Open button - adds an "Open URL in new tab" button (external-link icon) to the left of the existing Scrape button on every URL row. Disabled when the row is empty.
2. Width fix - the URLs field renders at col-lg-12 (full row) while every other field (Title, Studio Code, Date, Director, ...) renders at col-sm-3/col-sm-9. Bootstrap's percentages for these two don't map to a fixed pixel ratio (row gutter/negative-margin math differs), and Stash's own sidebar switches between a narrow fixed-width column and a much wider mobile-style layout at several different pixel thresholds - so a static CSS rule can't track it. Instead, fixUrlsWidth():
   • Detects whether Title's label and input are currently on the same line or stacked (compares their top position) and forces URLs' own row into the same mode via flex-wrap. This is a deliberate binary switch rather than relying on "does label+content width fit the row" - that emergent approach is rounding-sensitive and flips the wrong way right at Title's own wrap boundary (off-by-a-fraction-of-a-pixel vs Title's true sub-pixel layout).
   • Within that mode, matches Title's actual rendered label/input pixel widths so the sizes line up too.
   • Keeps clear of Stash's sidebar/video divider handle, which overlaps the last ~19px of any field that reaches the sidebar's right edge (true for Title too, just invisible there since it's not a button). Re-evaluated on every resize and DOM mutation.
3. Details tab relocation (setting, on by default) - hides the "URLs:" row on the File Info tab and shows it instead on the Details tab, directly under Tags. Reasoning: scene URLs aren't a property of the underlying file, so File Info isn't the right place for them.

How it works

All three are plain DOM manipulation (no React patch API used) driven by a MutationObserver on document.body, the same technique already used by this instance's own custom.js. Stash renders all scene tab panels at once and just toggles display:none, so the File Info content is always present in the DOM to read from/clone, even while viewing another tab.

• The open button is inserted into .input-group-append next to the .scrape-url-button, idempotently (checked by class name before inserting), so it survives re-renders.
• The Details-tab URLs block is a clone of the File Info <dd> content (the original is hidden via display:none, not removed/moved), which avoids fighting React's reconciliation over node ownership. It's re-synced (removed + re-cloned) only when the source content actually changes (tracked via a data-source-html marker), so it doesn't do wasteful work on every unrelated DOM mutation (e.g. video player ticks).
• If the scene has no Tags heading to anchor on, the block falls back to the end of the Details tab's content area.

Settings

• Show URLs on Details tab (instead of File Info) - BOOLEAN, defaults to off until saved; this instance has it explicitly saved to true.

Known limitation

Multiple scenes were spot-checked (with/without tags, performers, and descriptions) but this relies on Stash's current Details/File Info tab DOM structure (.scene-details, .file-info-panel, h6 text "Tag"/"Tags"). A future Stash UI rework could change this structure and require updating the selectors in sceneUrlEnhancements.js.