css: moved + tweaked styles to common.css

- Add baseline input[type="checkbox"] and input[type="radio"] styling
  in common.css (accent-color, size, cursor, flex-shrink)
- Give select a solid background (var(--bg-primary)) and its own focus rule
- Remove now-redundant checkbox accent-color/size from
  .admin-checkbox-label (form.css) and .param-checkbox (admin.css)
- Simplify .search-filter-select (repertoire.css) to inherit common
  select defaults (border, background, arrow icon)
- Keep all layout-specific classes in form.css and admin.css intact
- Add baseline input[type="checkbox"] and input[type="radio"] styling
  in common.css (accent-color, size, cursor, flex-shrink)
- Give select its own rule block with same shape as text inputs
  (transparent background, same padding/border/radius/focus)
- Remove now-redundant checkbox accent-color/size from
  .admin-checkbox-label (form.css) and .param-checkbox (admin.css)
- Simplify .search-filter-select (repertoire.css) to inherit common
  select defaults
- Keep all layout-specific classes in form.css and admin.css intact
- Remove bottom-border/border-radius:0 overrides from .admin-form,
  .admin-inline-form, .param-form, and .param-grid inputs/selects
- Change required-field indicator from border-bottom-style to
  border-style: dashed to work with full-border approach
- Update param-grid aria-invalid from border-bottom-color to border-color
- All text inputs, selects, and textareas now inherit the full-border
  style from common.css (border, border-radius, padding, focus ring)
- .password-gate input[password]: remove redundant padding override
- .retry-email-form input[email]: remove redundant border/border-radius/
  padding/box-sizing, keep only font-size (larger) and width
- .tfe-access-request-form input/textarea: remove broken references to
  undefined vars (--border, --background, --accent), now inherit from
  common.css. Remove redundant focus rule.
- .fhb-name-input: strip redundant padding/border/radius/font-size/font
- .admin-inline-form input/select: strip redundant font-size
- .param-checkbox: remove font-size (inherits from body)
- .param-checkbox small: remove redundant color + font-size (common.css small already sets both)
- .param-note: remove font-size
- .param-account-status: remove font-size
- .param-smtp-test-row label: remove display:block + font-size (common.css label)
- .param-smtp-status: remove font-size
- .param-grid label: remove font-size
- Remove .param-form legend padding override (now inherits common.css legend)
- Remove .param-danger-zone legend padding override
- Remove .param-export-zone legend padding override
- Remove .param-fieldset-inline legend entirely (only rule was padding)
- Remove .licence-explanation legend entirely (all properties identical to common.css legend)
- All fieldsets now consistently use common.css fieldset padding
  (0 var(--space-m) var(--space-m) var(--space-m))
- The common.css fieldset has padding-top: 0, which leaves checkboxes
  and other content tight against the legend. Add var(--space-s) top
  padding so the first content row has proper spacing from the legend.

app/public/assets/css/tfe.css

@@ -255,13 +255,6 @@ aside figcaption {
 .tfe-access-request-form input[type="email"],
 .tfe-access-request-form textarea {
     padding: var(--space-2xs) var(--space-3xs);
-    border-color: var(--border);
-    background: var(--background);
-}
-
-.tfe-access-request-form input[type="email"]:focus,
-.tfe-access-request-form textarea:focus {
-    border: 2px solid var(--accent);
 }
 
 .tfe-btn-request-access {