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/form.css

@@ -31,7 +31,7 @@
   font-weight: 400;
 }
 
-/* ── Inputs, selects, textareas (admin forms use bottom-border style) ──── */
+/* ── Inputs, selects, textareas ──────────────────────────────────────────── */
 .admin-form
   input:not([type="checkbox"]):not([type="radio"]):not([type="file"]):not(
     [type="hidden"]
@@ -42,34 +42,12 @@
 .admin-inline-form input[type="number"],
 .admin-inline-form select {
   width: 100%;
-  border: none;
-  border-bottom: 1px solid var(--border-primary);
-  border-radius: 0;
-  padding: var(--space-3xs) 0;
-}
-
-.admin-form
-  input:not([type="checkbox"]):not([type="radio"]):not([type="file"]):not(
-    [type="hidden"]
-  ):not([type="submit"]):focus,
-.admin-form select:focus,
-.admin-form textarea:focus,
-.admin-inline-form input:focus,
-.admin-inline-form select:focus {
-  border-bottom: 2px solid var(--accent-primary);
 }
 
 .admin-form textarea {
   min-height: 100px;
 }
 
-/* Select custom arrow overrides for bottom-border style */
-.admin-form select,
-.admin-inline-form select {
-  background-position: right 0 center;
-  padding-right: 1.2rem;
-}
-
 /* ── Required-field indicators ──────────────────────────────────────────── */
 .admin-form
   input:not([type="checkbox"]):not([type="radio"]):not([type="file"]):not(
@@ -77,7 +55,7 @@
   ):not([type="submit"]):required,
 .admin-form select:required,
 .admin-form textarea:required {
-  border-bottom-style: dashed;
+  border-style: dashed;
 }
 
 .admin-form
@@ -168,13 +146,6 @@
   cursor: pointer;
 }
 
-.admin-checkbox-label input[type="checkbox"] {
-  accent-color: var(--accent-primary);
-  width: 14px;
-  height: 14px;
-  cursor: pointer;
-}
-
 /* ── Fieldsets & legends ────────────────────────────────────────────────── */
 /* Base fieldset/legend styles live in common.css */
 .admin-body fieldset,
@@ -355,15 +326,6 @@
   margin: 0;
 }
 
-.licence-explanation legend {
-  font-size: var(--step--1);
-  font-weight: 600;
-  letter-spacing: 0.04em;
-  text-transform: uppercase;
-  color: var(--text-secondary);
-  padding: 0 var(--space-2xs);
-}
-
 .licence-info h3 {
   margin-top: var(--space-m);
 }
@@ -479,7 +441,6 @@
 
 .password-gate input[type="password"] {
   width: 100%;
-  padding: var(--space-xs);
   margin: var(--space-2xs) 0 var(--space-s);
 }
 
@@ -1021,12 +982,8 @@ a.recap-file-name:hover {
 }
 
 .retry-email-form input[type="email"] {
-  padding: var(--space-xs) var(--space-s);
-  border: 1px solid var(--border-primary);
-  border-radius: var(--radius);
   font-size: var(--step-0);
   width: 100%;
-  box-sizing: border-box;
 }
 
 .retry-email-form input.input-error {