chore(deps): Tailwind 4 (#5021)

Renovate's tailwindcss bump (PR #150) plus the migration it needs:

- Theme moves from tailwind.config.js into app.css as `@theme inline`,
  mapping the same FabledSword tokens. tailwind.config.js is gone.
- PostCSS runs @tailwindcss/postcss; autoprefixer is dropped, since
  Tailwind 4 prefixes through Lightning CSS.
- Class renames from @tailwindcss/upgrade 4.3.3, reviewed: outline-none
  -> outline-hidden, focus-visible:outline -> outline-solid, shadow ->
  shadow-sm, shadow-sm -> shadow-xs, flex-shrink-0 -> shrink-0. Bare
  `rounded` stays: v4 keeps it at 0.25rem, as before.
- Three v3 preflight defaults kept in a base layer so nothing changes on
  screen: gray-200 default border colour, gray-400 placeholder text and
  the pointer cursor on buttons.
- The unused class-based dark variant is not carried over; no template
  uses `dark:`.

Clears the five high and two moderate npm audit findings that came in
through Tailwind 3 (braces, chokidar, micromatch, fast-glob,
postcss-selector-parser).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/lib/components/ReacquisitionSettingsCard.svelte

@@ -127,7 +127,7 @@
           max="720"
           bind:value={form.grace_hours}
           class="mt-1 w-28 rounded border border-border bg-background px-2 py-1 text-sm
-                 text-text-primary focus-visible:outline focus-visible:outline-2
+                 text-text-primary focus-visible:outline-solid focus-visible:outline-2
                  focus-visible:outline-accent"
         />
       </label>
@@ -144,7 +144,7 @@
           max="10"
           bind:value={form.max_attempts}
           class="mt-1 w-28 rounded border border-border bg-background px-2 py-1 text-sm
-                 text-text-primary focus-visible:outline focus-visible:outline-2
+                 text-text-primary focus-visible:outline-solid focus-visible:outline-2
                  focus-visible:outline-accent"
         />
       </label>
@@ -157,7 +157,7 @@
           max="168"
           bind:value={form.backoff_base_hours}
           class="mt-1 w-28 rounded border border-border bg-background px-2 py-1 text-sm
-                 text-text-primary focus-visible:outline focus-visible:outline-2
+                 text-text-primary focus-visible:outline-solid focus-visible:outline-2
                  focus-visible:outline-accent"
         />
       </label>
@@ -170,7 +170,7 @@
           max="720"
           bind:value={form.backoff_max_hours}
           class="mt-1 w-28 rounded border border-border bg-background px-2 py-1 text-sm
-                 text-text-primary focus-visible:outline focus-visible:outline-2
+                 text-text-primary focus-visible:outline-solid focus-visible:outline-2
                  focus-visible:outline-accent"
         />
       </label>
@@ -186,7 +186,7 @@
           max="200"
           bind:value={form.max_per_pass}
           class="mt-1 w-28 rounded border border-border bg-background px-2 py-1 text-sm
-                 text-text-primary focus-visible:outline focus-visible:outline-2
+                 text-text-primary focus-visible:outline-solid focus-visible:outline-2
                  focus-visible:outline-accent"
         />
       </label>
@@ -213,7 +213,7 @@
            watching those rows never get a request would reasonably conclude
            the feature is broken. -->
       <p class="flex items-start gap-2 rounded-md bg-surface-hover px-3 py-2 text-xs text-text-secondary">
-        <TriangleAlert size={14} class="mt-0.5 flex-shrink-0 text-action-destructive" aria-hidden="true" />
+        <TriangleAlert size={14} class="mt-0.5 shrink-0 text-action-destructive" aria-hidden="true" />
         <span>
           {saved.unnameable_albums}
           {saved.unnameable_albums === 1 ? 'album has' : 'albums have'} missing files but no
@@ -227,7 +227,7 @@
       <button
         type="button"
         class="rounded-md bg-action-secondary px-4 py-2 text-sm text-action-fg hover:opacity-90
-               focus-visible:outline focus-visible:outline-2 focus-visible:outline-accent
+               focus-visible:outline-solid focus-visible:outline-2 focus-visible:outline-accent
                disabled:cursor-not-allowed disabled:opacity-50"
         disabled={!dirty || saving}
         onclick={save}