fix: compare in UTC and detect moved and reordered pages

[andresvillenas]

Fixes the accuracy gaps found in the foundation design review: time zones, moved and reordered pages, and clearer guidance for editors.

Changes

• Time zones (bug).
  • Before: Xperience stores dates in the server's local time, and the inventory endpoint sent them without a time zone, so a source and target in different time zones compared the wrong moments.
  • Now: both inventories convert to UTC, the endpoint sends dates with a Z suffix, and the schema version is 2. A date without a time zone (from a target on schema version 1) is read as this server's local time, the same as before, so mixed versions behave as they did.
• Moved and reordered pages. Moving or reordering a page changes neither its version nor its publish date, so the date comparison couldn't see it.
  • Moved: a different tree path on the target → Out of date on target.
  • Reordered: for each level, the pages present on both sides are compared by relative order; if it differs, those pages become Out of date. The whole level is marked because Kentico requires all pages on the level to be synced to transfer an order change. Comparing relative order means a page that exists on only one side doesn't cause false positives.
  • The inventory now carries each page's order.
• Reasons and tooltips. Each status item carries a Reason (newer here, publish state, moved, reordered). The status tooltip explains it and what to sync. For items only on the target, the tooltip explains that Content Sync can't delete, so they have to be deleted on the target.
• Dates in the editor's time zone. The Last published column uses the same local date-time cell as Kentico's own listings. Its C# helper is internal, so the cell is built with the same component name, which is noted in the spec as a convention covered by the two-version check.
• Example host. Content Sync packages are excluded from DancingGoat's content items; their JSON files were included twice and broke the build after a real sync.
• Docs.
  • Foundation spec: time zones, the move and reorder rules, deletions, and why content fingerprints and triggering a sync are deferred.
  • Admin page spec: tooltips, dates, and the date filter's server-time days.
  • Usage Guide: moved, reordered and deleted items, time zones, and what the page can't see (edits on the target, scheduled publishing).

Testing

• 181 unit tests pass (new: UTC conversion, schema 1 and 2 dates over the wire, move and reorder rules including the shifted-order case, reasons, tooltips).
• Verified live on 31.7.2:
  • the endpoint sends schema 2 with UTC dates and page order;
  • the Last published column renders like the Content hub's date column;
  • reordering two pages in the source's page tree left both publish dates unchanged and marked the Articles level Out of date with the reorder tooltip;
  • a source-only page on that level stayed Missing;
  • moving the page back restored In sync.
• Not verified live: moving a page to another parent. Dancing Goat's page type restrictions only allow article pages under Articles; the rule is covered by unit tests.