fix(scss): remove forbidden @import "variables" lines breaking V19 asset bundle

Phases 1-3's SCSS files used '@import "variables";' to pull in tokens
from _variables.scss. V19's odoo.addons.base.models.assetsbundle
forbids cross-file SCSS imports for security ('Local import forbidden')
and the asset bundle warning was firing on every web request.

Phase 4 caught + fixed this for fusion_accounting_followup; Phases 1-3
were never updated. Today's deployment surfaced the CSS error reported
by the user.

Resolution:
- Removed @import lines from 7 SCSS files across bank_rec, reports, assets
- Variables come from _variables.scss via manifest concatenation order
  (bundle order is _variables.scss first, then dependent files)
- Replaced documentation comments to NOT contain the literal string
  '@import "variables"' \u2014 Odoo's check is regex-based and was
  matching even SCSS comments

Verified clean: bundle rebuilds with zero 'Local import forbidden'
warnings; all 534 fusion-module tests still pass.

Made-with: Cursor

fusion_accounting_assets/static/src/scss/assets.scss

@@ -1,4 +1,5 @@
-@import "variables";
+// Variables come from _variables.scss via manifest concatenation order.
+// (V19 forbids cross-file SCSS imports; rely on bundle order instead.)
 
 .o_fusion_assets {
     background: $asset-bg-secondary;

fusion_accounting_assets/static/src/scss/dark_mode.scss

@@ -1,4 +1,4 @@
-@import "variables";
+// Variables come from _variables.scss via manifest concatenation order.
 
 [data-color-scheme="dark"] .o_fusion_assets {
     background: #1f2937; color: #f9fafb;

fusion_accounting_bank_rec/static/src/scss/ai_suggestion.scss

@@ -1,4 +1,4 @@
-@import "variables";
+// Variables come from _variables.scss via manifest concatenation order.
 
 // ============================================================
 // AI Suggestion strip (inline, on each statement line card)

fusion_accounting_bank_rec/static/src/scss/bank_reconciliation.scss

@@ -1,4 +1,5 @@
-@import "variables";
+// Variables come from _variables.scss via manifest concatenation order.
+// (V19 forbids cross-file SCSS imports; rely on bundle order instead.)
 
 // ============================================================
 // Bank reconciliation kanban container

fusion_accounting_bank_rec/static/src/scss/dark_mode.scss

@@ -1,5 +1,4 @@
-@import "variables";
-
+// Variables come from _variables.scss via manifest concatenation order.
 // Activated via [data-color-scheme="dark"] on body or any ancestor.
 // Mirrors Odoo's standard dark-mode trigger pattern.
 

fusion_accounting_reports/static/src/scss/dark_mode.scss

@@ -1,4 +1,4 @@
-@import "variables";
+// Variables come from _variables.scss via manifest concatenation order.
 
 [data-color-scheme="dark"] .o_fusion_reports {
     background: #1f2937;

fusion_accounting_reports/static/src/scss/reports.scss

@@ -1,4 +1,5 @@
-@import "variables";
+// Variables come from _variables.scss via manifest concatenation order.
+// (V19 forbids cross-file SCSS imports; rely on bundle order instead.)
 
 .o_fusion_reports {
     background: $report-bg-secondary;