[FIX] iap_mail: enrichment tags illegible in dark mode

In the lead's enrichment, the fields containing tags have an hardcoded
background for some reason... which, in dark mode, makes the tags' label
illegible (as it is a light text on light background).

This commit fixes it by forcing a darker gray when rendered in dark mode
(where the dark mode's bundle is applied, like in the backend).

Steps to reproduce:
- Open CRM
- Create an opportunity using a well-known domain in the email address
  (for example)
- Click "Enrich"
- A card appears in the chatter containing the matching company's
  information
- Switch to dark mode
=> Sectors, Technologies Used... tags keep the light background

opw-3678598

closes odoo/odoo#149409

Signed-off-by: Samuel Degueldre (sad) <sad@odoo.com>

addons/iap_mail/__manifest__.py

@@ -22,6 +22,9 @@
             'iap_mail/static/src/js/**/*',
             'iap_mail/static/src/scss/iap_mail.scss',
         ],
+        "web.dark_mode_assets_backend": [
+            'iap_mail/static/src/scss/iap_mail.dark.scss',
+        ],
     },
     'license': 'LGPL-3',
 }

addons/iap_mail/static/src/scss/iap_mail.dark.scss

@@ -0,0 +1,3 @@
+.o_partner_autocomplete_enrich_info label {
+    background-color: var(--gray-white-25) !important;
+}