feat(ui): Page.SettingsActions for settings save bar (#819)

* feat(ui): add Page.SettingsActions for settings save bar

Introduce a sticky bottom save/discard bar on Page and migrate settings
pages to use it instead of header or inline save buttons. Includes
profile, org, customize-lms, notifications, auth, AI tutor, course
settings, certificates, and cohort settings.

Co-authored-by: Rotimi Best <[email protected]>

* fix(ui): always show Page.SettingsActions, disable when clean

Keep the settings save bar visible at all times and disable Save and
Discard when hasChanges is false instead of hiding the bar entirely.

Co-authored-by: Rotimi Best <[email protected]>

* fix(ui): add bottom spacing and shadow to Page.SettingsActions

Wrap the actions card in a sticky container with bottom padding so it
does not sit flush against the viewport edge, and use shadow-md on the
card for clearer elevation.

Co-authored-by: Rotimi Best <[email protected]>

* fix(ui): stop viewport-sticking Page.SettingsActions on scroll

Remove sticky bottom positioning so the save bar stays at the end of the
page content and scrolls away when viewing upper sections.

Co-authored-by: Rotimi Best <[email protected]>

* fix(ui): use sticky bottom for Page.SettingsActions dock behavior

Replace the IntersectionObserver fixed/dock toggle that caused layout
thrashing and flipping with native position: sticky; bottom: 0. Move
overflow-x-hidden from Page.Root to Page.Body so sticky is not broken.

Co-authored-by: Rotimi Best <[email protected]>

* fix(ui): keep Page.SettingsActions sticky and above editor content

Page.Root carried md:overflow-x-auto, which makes overflow-y compute to
auto, turning the root into the sticky bar's nearest scrolling ancestor.
Since the root sizes to its content it never scrolls internally, so the
bar rendered at its natural flow position instead of pinning to the
viewport. Drop the overflow so sticky resolves against the viewport;
horizontal containment stays on Page.Body.

Raise the bar to z-50 so it is not painted over by the editor root,
which is relative z-50. Matching rather than exceeding 50 keeps
body-portaled dialogs and sheets above the bar.

Show the shadow only while the bar is pinned away from its flow
position, tracked with an IntersectionObserver on a 1px sentinel
sibling. Unlike the previous observer this toggles a box-shadow only, so
it cannot feed back into layout.

* fix(ui): tighten settings actions spacing and tab visibility

- Remove mt-6 and lower z-index so popovers sit above the bar
- Wrap sentinel in a single root to avoid extra Page.Root flex gap
- Remove Page.Body mb-4 redundant with settings actions spacing
- Show certificate save bar only on the settings tab
- Raise theme color picker z-index via --picker-z-index

Co-authored-by: Rotimi Best <[email protected]>

* fix(dashboard): address PR review feedback for settings actions

- Capture profile/org saved baselines only on initial load, not on edits
- Reset course settings errors with explicit field shape in handleDiscard
- Restore VisitOrgSiteButton on org profile settings header
- Derive AI tutor dirty state from stores directly instead of mirrored state
- Use discard-specific French label and document SettingsActions props

Co-authored-by: Rotimi Best <[email protected]>

* docs(ui): clarify Page.Root ownership for Page.SettingsActions

"Last child of Page.Root" is a runtime relationship. Several settings
pages get their Page.Root from a +layout.svelte, so the page file holds
only Page.Header, Page.Body, and Page.SettingsActions. Document that this
is correct and list the pages, since adding a nested Page.Root stacks two
min-height containers and shortens the sticky bar's containing block.

Also document that Page.SettingsActions must never be rendered from
inside Page.Body: overflow-x-hidden makes Page.Body a scroll container
that never scrolls, so a sticky bar in it has no travel.

---------

apps/dashboard/src/lib/utils/translations/da.json

@@ -2,8 +2,11 @@
   "common": {
     "refresh": "Opdater",
     "unsaved_changes": {
-      "message": "Du har ikke-gemte ændringer. Er du sikker på, at du vil tage afsted?"
-    }
+      "message": "Du har ikke-gemte ændringer. Er du sikker på, at du vil tage afsted?",
+      "label": "Ikke-gemte ændringer"
+    },
+    "discard": "Kassér",
+    "save_changes": "Gem ændringer"
   },
   "validations": {
     "generic": {