Fill & Sign: date format and date language in Preferences (refs #158) (#505)

* M5.7: date format and date language for Fill & Sign in the engine

* M5: flatten Fill & Sign marks when saving

Saving can now bake typed text, marks and signatures into the page, from Preferences or doc_save. The option defaults off, so a normal save still leaves them editable, and other comments and form fields stay.

* M4: zoom the Organize page grid

The page grid draws its pages at 50% to 300%: toolbar buttons with a
percentage that resets to 100%, trackpad pinch or Ctrl/⌘ + wheel about
the page under the pointer, and ⌘+ / ⌘− / ⌘0 (which no longer change the
hidden page view's zoom while the grid shows).

Thumbnails are re-rendered sharper in a few steps as the grid grows,
capped so one document's thumbnails stay within 256 MB. The page under
the pointer (or the first one in view) stays where it is across a zoom.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* M4: zoomed grid pages are rendered at the size drawn

A zoomed page grid stretched 132 pt thumbnails, and the stepped detail
that was meant to help was capped by a memory budget, so a long document
stayed blurry at any zoom.

Pages drawn larger than their thumbnails now get a render at exactly the
size drawn while they are in view; the thumbnail stands in until it
arrives. Only pages in view keep one, so memory no longer depends on the
page count, and thumbnails go back to their one fixed size.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* M5.7: fill_sign_date_format tool; format and language on fill_sign_add

* M5.7: Preferences ▸ Date format for Fill & Sign dates (refs #158)

* M5.7: refuse Fill & Sign dates the PDF text font can't hold

* M5.7: Spanish labels for Preferences ▸ Date format

* View: the middle button pans instead of drawing with markup tools

egui's drag responses accept every pointer button, so on Windows and macOS a
middle-button drag reached the page tools: with Draw (ink) selected it drew a
stroke, and other tools cropped, selected or moved. Linux was unaffected
because its middle-click auto-scroll already blocks page input.

Outside Linux a middle-button drag that starts in the viewport (document or
Organize Pages) now pans 1:1 while the button is held, with a Grabbing
cursor, and page input is blocked from the press through the release. Linux
keeps its latched auto-scroll.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* M3: a short page gone to from the Pages panel stays current

The current page was whichever page showed most of itself. Going to a short
page (a cheque) above a tall one scrolls it to the top, where the tall page
below shows more, so the current page and the Pages panel's highlight moved
to the tall page instead of the one clicked. The page navigated to now stays
current while it is wholly on screen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* M4: page operations from the Pages panel: context menu and drag to reorder

Right-clicking a thumbnail offers Extract pages, Cut, Copy and Paste after, on
the selection or on the page clicked (which becomes the selection), as the
organize grid does. Dragging thumbnails moves the selection, or the page
grabbed, to the gap it is dropped on: a bar marks the gap, the page count
follows the pointer, and the panel scrolls near its edges. The move is one
undoable step; the moved pages stay selected and the current page follows
its page. Documents that forbid assembly keep click-only thumbnails.

Parity: view.thumbnail-context-ops is shipped, with what it still lacks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Pages panel: only the primary button drags thumbnails; a drag left over after the panel closed or the document changed is dropped

* Fill & Sign dates: German, Bulgarian, Hungarian and Ukrainian month and weekday names, matching the interface languages

---------

Co-authored-by: Mark Bartalos <bartalos86@gmail.com>
Co-authored-by: samehelhawary <basio20044@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Cody Vogt <Cody.Vogt@caltechsurveys.com>
Co-authored-by: William Max & Co. <info@williammax.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>

parity/acrobat-features.toml

@@ -5213,9 +5213,9 @@ tier = "P0"
 milestone = "M5"
 status = "shipped"
 commands = ["sign.fill.date"]
-tools = ["fill_sign_add"]
-evidence = ["crates/ui-egui/tests/fill_sign.rs::text_marks_and_date", "crates/automation/tests/automation.rs::fill_and_sign_through_tools"]
-notes = "local date, m/d/yyyy"
+tools = ["fill_sign_add", "fill_sign_date_format"]
+evidence = ["crates/ui-egui/tests/fill_sign.rs::text_marks_and_date", "crates/automation/tests/automation.rs::fill_and_sign_through_tools", "crates/ui-egui/tests/date_format.rs::fill_and_sign_dates_follow_the_date_format_preference_and_it_is_remembered", "crates/engine/src/dates.rs::presets_write_the_day_in_their_own_order", "crates/engine/src/dates.rs::names_follow_the_date_language", "crates/ui-egui/tests/date_format.rs::month_names_follow_the_date_language_or_else_the_interface_language", "crates/ui-egui/tests/date_format.rs::a_date_the_pdf_cannot_hold_is_refused_with_a_warning_first"]
+notes = "local date in Preferences ▸ Date format (default m/d/yyyy; 12 presets or any pattern in Acrobat date letters with \\ escapes, checked and previewed as typed, remembered; only whole date codes accepted; month and weekday names in the interface languages, Czech months in the genitive after a day, following the interface language unless one is picked; fill_sign_add takes a one-off format and language). Beyond Acrobat: its Fill & Sign has no format setting (only Acrobat Sign accounts do). Missing: Fill & Sign text is Helvetica/WinAnsi, so a date with letters outside Western European (Czech ř, Japanese, Chinese names) is refused with a warning instead of being saved as ?; the OS locale's format isn't offered as a preset; names in languages without an interface translation"
 
 [[feature]]
 id = "form.fill-sign-signature"