Add sous-traitant, salaire/stage, and charges local pro ligne types

Three new field_type_ligne values (config/sync +
figli_compta_ledger.install for fresh-install parity), wired through
every place that enumerates the type list: LedgerActionsController's
inline type-change endpoint, home.js's type dropdown/badge, dashboard.js's
per-type chart, home.css's badge colors.

Sous-traitant is linkable to field_entree_liee (pays out against a
client's work, like versement/achat); salaire/stage and charges local
pro are not (structural costs, like charge). Turns out 13 lines
already carried "salaire_stage" and 1 "sous_traitant" as raw field
values from the historical migration -- list_string doesn't enforce
allowed_values at the storage level, so they saved fine but had no
label and weren't selectable in the UI until now.

Also fixes a real bug this surfaced: filtering /lignes by a sparse
type (e.g. "Autre") silently broke the sliding window -- so few rows
matched that the table no longer overflowed, so it never fired another
'scroll' event, so loadOlder()/loadNewer() never ran again ("les lignes
antérieures ne chargent plus"). Added ensureScrollable(), which keeps
extending the window in both directions whenever a thinning filter
(compte/client/type/écarts) leaves too little to scroll, and widened
the trim cap while filtering (MAX_LOADED_MONTHS_FILTERED) since the
normal 30-month cap actively fights a sparse filter -- extending one
end and immediately trimming the other nets out to nearly the same
slice every round. Bounded by a round counter rather than "did the
window stop moving": addMonths() uses Date#setMonth(), which isn't
invertible for month-end dates, so the window can drift indefinitely
in tiny steps without ever exactly repeating.

Verified: filtering by "Autre" now finds 24 matches (was stuck at 1)
and the view becomes scrollable within ~17s, settling cleanly rather
than hanging.

config/sync/field.storage.node.field_type_ligne.yml

@@ -32,6 +32,15 @@ settings:
     -
       value: hebergement
       label: Hébergement
+    -
+      value: sous_traitant
+      label: Sous-traitant
+    -
+      value: salaire_stage
+      label: 'Salaire / stage'
+    -
+      value: charges_local_pro
+      label: 'Charges local pro'
   allowed_values_function: ''
 module: options
 locked: false