docs(adr): convert all ADRs to MADR 2.1.2 format

Rewrites all 12 frontend ADRs from a custom structure to the MADR 2.1.2
template required by the VS Code ADR Manager extension: bullet metadata
(Status/Date), standardised section headings, "Chosen option: X, because Y"
wording, and explicit Pros/Cons blocks per option.

docs/decisions/0012-scss-bootstrap-import-deprecation.md

@@ -1,29 +1,57 @@
-# ADR 0012: SCSS Strategy — Bootstrap Variable Overrides and Sass @import Deprecation
+# Silence the Sass @import deprecation for the Bootstrap import chain
 
-**Date:** 2026-04-26
-**Status:** Accepted (workaround pending Bootstrap 6)
+- Status: accepted
+- Date: 2026-04-26
 
-## Context
+## Context and Problem Statement
 
-Bootstrap 5 relies on Sass's `@import` rule and `!default` variable overrides: our custom `_variable.scss` must be loaded before Bootstrap's `variables.scss` so that Bootstrap picks up our values via `!default`.
+Bootstrap 5 relies on Sass's `@import` rule and `!default` variable overrides: our custom `_variable.scss` must be loaded before Bootstrap's `variables.scss` so that Bootstrap picks up our values via the `!default` mechanism. Dart Sass 1.80+ deprecates `@import` in favour of the `@use` module system. How should the deprecation be addressed?
 
-Dart Sass 1.80+ deprecates `@import` in favour of the `@use` module system. The `@use` system uses isolated module scopes, which breaks the `!default` override mechanism: variables loaded via `@use` in our file do not flow into Bootstrap's module scope.
+## Decision Drivers
 
-Migrating to `@use` for the Bootstrap import chain would require either:
+- Bootstrap 5's `!default` override mechanism is incompatible with `@use` module scopes — variables loaded via `@use` do not flow into Bootstrap's module scope.
+- Other Dart Sass deprecations (`color.red/green/blue()`, global `if()`) were fixed properly.
 
-- Waiting for Bootstrap 6, which is expected to adopt `@use` natively.
-- Rewriting the entire Bootstrap variable override mechanism using `@use "bootstrap" with (...)`.
+## Considered Options
 
-Neither option is viable in the short term.
+- Silence the `@import` deprecation via `angular.json`
+- Migrate to `@use` with `@use "bootstrap" with (...)`
+- Wait for Bootstrap 6
 
-## Decision
+## Decision Outcome
 
-- Suppress the Sass `@import` deprecation warning in `angular.json` via `stylePreprocessorOptions.sass.silenceDeprecations: ["import"]`.
-- Keep the existing `@import`-based Bootstrap loading chain intact.
-- Fix other Dart Sass deprecations properly: `color.red/green/blue()` replaced with `color.channel()`, global `if()` replaced with `@if`/`@else`.
+Chosen option: "Silence the `@import` deprecation via `angular.json`", because the `@use` migration is blocked by Bootstrap 5's architecture and Bootstrap 6 (which adopts `@use` natively) is not yet released.
 
-## Consequences
+The deprecation is suppressed in `angular.json` via `stylePreprocessorOptions.sass.silenceDeprecations: ["import"]`. The existing `@import`-based Bootstrap loading chain is kept intact. All other Dart Sass deprecations are fixed properly.
 
-- **Positive:** Bootstrap customisation works correctly with no behaviour change.
-- **Negative:** Deprecation silenced rather than fixed. `@import` will be removed in Dart Sass 3.0.
-- **Future action:** When Bootstrap 6 is released with `@use` support, migrate the import chain and remove the `silenceDeprecations` entry. Supersede this ADR at that point.
+### Positive Consequences
+
+- Bootstrap customisation works correctly with no behaviour change.
+- No risk of introducing regressions by attempting an incompatible migration now.
+
+### Negative Consequences
+
+- Deprecation is silenced rather than fixed. `@import` will be removed in Dart Sass 3.0.
+
+## Pros and Cons of the Options
+
+### Silence the `@import` deprecation
+
+- Good, because no behaviour change — existing variable overrides continue to work.
+- Bad, because the underlying issue is deferred, not resolved.
+
+### Migrate to `@use` with `@use "bootstrap" with (...)`
+
+- Good, because fully resolves the deprecation.
+- Bad, because requires rewriting all Bootstrap variable overrides using `with ()` syntax — significant effort.
+- Bad, because the `with ()` syntax has limitations compared to `!default` chaining.
+
+### Wait for Bootstrap 6
+
+- Good, because Bootstrap 6 adopts `@use` natively — migration path will be documented by the Bootstrap team.
+- Bad, because Bootstrap 6 release date is unknown; deferring means living with the silenced warning.
+
+## Links
+
+- Related to [ADR 0003](0003-dual-ui-library-progressive-migration.md)
+- Future action: when Bootstrap 6 is released with `@use` support, migrate the import chain, remove the `silenceDeprecations` entry, and supersede this ADR.