🎨 (basic): Organiza estilos de Basic e Intro

Divide `basic.css` en parciales SCSS bajo `assets/scss/basic/`, integra
`normalize.css` en `basic.min.css` y compila `intro.scss` por separado a
`intro.min.css`.

assets/scss/basic/_pager.scss

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+.pager {
+    display: flex;
+    flex-wrap: wrap;
+    align-items: center;
+    gap: 1rem;
+    margin: 1rem 0;
+    padding: 0 1rem;
+}
+.pager-align-start {
+    justify-content: flex-start;
+}
+.pager-align-center {
+    justify-content: center;
+}
+.pager-align-end {
+    justify-content: flex-end;
+}
+.pager-summary {
+    color: var(--val-color--text--muted);
+    font-size: 0.8125rem;
+    align-self: flex-start;
+    margin-inline-end: auto;
+}
+.pager-align-start .pager-summary {
+    order: 1;
+    margin-inline-end: 0;
+    margin-inline-start: auto;
+}
+.pager-align-center .pager-summary {
+    order: 1;
+    flex-basis: 100%;
+    text-align: center;
+    margin-inline-end: 0;
+}
+
+.pagination {
+    display: flex;
+    align-items: center;
+    gap: 0.25rem;
+    list-style: none;
+    margin: 0;
+    padding: 0;
+}
+.pagination a {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    min-width: 1.5rem;
+    padding: 0.375rem 0.625rem;
+    border-radius: 0.375rem;
+    color: var(--val-color--text);
+    text-decoration: none;
+}
+.pagination a:hover {
+    background-color: color-mix(in srgb, var(--val-color--text) 8%, transparent);
+}
+.pagination .active a {
+    color: #fff;
+    background-color: var(--val-color--primary);
+}
+.pagination .disabled a {
+    color: var(--val-color--text--muted);
+    pointer-events: none;
+    cursor: default;
+}
+
+.page-ellipsis {
+    padding: 0.375rem 0.25rem;
+    color: var(--val-color--text--muted);
+}
+
+// .page-link-icon shows the navigation text of the previous/next buttons. The full accessible text
+// goes separately, in the link's aria-label. So replacing the visible text with other content does
+// not affect accessibility, e.g. to use "‹"/"›" you can apply:
+//
+// .page-link-icon {
+//     display: inline-block;
+//     font-size: 0;
+// }
+// .page-previous .page-link-icon::before {
+//     content: "‹";
+//     font-size: 1rem;
+//     display: inline-block;
+//     transform: translateY(-0.15em) scale(1.5);
+// }
+// .page-next .page-link-icon::before {
+//     content: "›";
+//     font-size: 1rem;
+//     display: inline-block;
+//     transform: translateY(-0.15em) scale(1.5);
+// }
+
+.pager-jump {
+    display: flex;
+    align-items: center;
+}
+.pager-jump:focus-within {
+    border-radius: 0.375rem;
+    box-shadow: 0 0 0 0.2rem color-mix(in srgb, var(--val-color--primary) 25%, transparent);
+}
+.pager-jump-input > input.form-control:focus,
+.pager-jump-button:focus {
+    outline: none;
+    box-shadow: none;
+}
+.pager-jump-input > input.form-control {
+    width: calc(var(--pager-jump-width, 1ch) + 2.5rem);
+    padding: 0.375rem 0.625rem;
+    line-height: var(--val-lh--base);
+    border: 0;
+    border-start-end-radius: 0;
+    border-end-end-radius: 0;
+    background-color: var(--val-color--bg--muted);
+}
+.pager-jump-input > input.form-control {
+    text-align: center;
+    appearance: textfield;
+    -moz-appearance: textfield;
+}
+.pager-jump-input > input.form-control::-webkit-outer-spin-button,
+.pager-jump-input > input.form-control::-webkit-inner-spin-button {
+    -webkit-appearance: none;
+    margin: 0;
+}
+.pager-jump-button {
+    padding: 0.375rem 0.625rem;
+    border: 0;
+    border-start-start-radius: 0;
+    border-end-start-radius: 0;
+}
+.pager-jump-button:hover {
+    background-color: color-mix(in srgb, var(--val-color--primary) 85%, black);
+}