fix(quick-look): dark-mode-aware instructions panel

The Operator Instructions panel had a hardcoded inline style
(background: #f8f9fa) which became a white-on-dark unreadable blob
in dark mode. Replaced with a CSS class backed by an SCSS file that
branches at compile-time via $o-webclient-color-scheme — registered
in both web.assets_backend (light) and web.assets_web_dark (dark)
bundles per the CLAUDE.md pattern.

Tokens: panel bg #f8f9fa light / #22262d dark; border #d8dadd /
#3a3f47; text #212529 / #e8eaed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_jobs/views/fp_job_form_inherit.xml

@@ -83,6 +83,10 @@
                           decoration-warning="state == 'paused'"
                           decoration-muted="state in ('skipped', 'cancelled')">
                         <field name="sequence" widget="handle"/>
+                        <button name="action_open_quick_look" type="object"
+                                title="View step details"
+                                icon="fa-info-circle"
+                                class="btn-link"/>
                         <field name="name"/>
                         <field name="work_centre_id" optional="show"/>
                         <field name="tank_id" optional="hide"/>

fusion_plating/fusion_plating_jobs/views/fp_job_step_quick_look_views.xml

@@ -58,7 +58,7 @@
                     </div>
 
                     <separator string="Operator Instructions"/>
-                    <div style="max-height: 40vh; overflow: auto; padding: 8px; background: #f8f9fa; border: 1px solid #d8dadd; border-radius: 4px;">
+                    <div class="o_fp_quick_look_instructions">
                         <field name="quick_look_instructions" nolabel="1" readonly="1"/>
                     </div>
                     <p class="text-muted small"