feat(design): the field family, the dropdown trigger, native controls, the no-raw-input lint rule (E28 S3c)

- ui/Input, Textarea, InnerInput + fieldClass (A4): the >= 3:1 edge, a 2px accent
  focus edge, the danger edge for invalid, md/sm/xs/heading rungs, 1rem and 44 on touch
- ui/SelectTrigger (A5): SortControl, FilterSelect, the view switcher and the date
  filter on one trigger, a pill in a toolbar, r8 in a form
- ui/NativeControls (A6): Checkbox, CheckRow, Slider, ColorInput
- every raw input swept (~100 sites); inputCls retired; local/input-primitive
- useReturnFocus: an in-place editor hands the focus back to its trigger on
  Enter/Escape (the playlist and Plex title renames, the priority number);
  the Plex playlist rename gains Escape and an accessible name
- back to top: a round 48 FAB (owner decision); DESIGN.md A2 and the log

frontend/src/components/SetupWizard.tsx

@@ -5,7 +5,7 @@ import { api, HttpError } from "../lib/api";
 import { setLanguage, type LangCode } from "../i18n";
 import LanguageSwitcher from "./LanguageSwitcher";
 import { Button } from "./ui/Button";
-import { inputCls } from "./ui/form";
+import { Input } from "./ui/Input";
 
 // First-run install wizard. Shown by App.tsx while the instance is unconfigured. The one-time
 // setup token comes from the URL the app printed to the container logs (?token=…); every step
@@ -165,38 +165,38 @@ export default function SetupWizard() {
 
           {step === "admin" && (
             <Section title={t("setup.admin.title")} desc={t("setup.admin.desc")}>
-              <input
+              <Input
+                className="w-full"
                 type="email"
                 value={email}
                 onChange={(e) => setEmail(e.target.value)}
                 placeholder={t("setup.admin.email")}
                 autoComplete="username"
-                className={inputCls}
               />
-              <input
+              <Input
+                className="w-full"
                 type="password"
                 value={password}
                 onChange={(e) => setPassword(e.target.value)}
                 placeholder={t("setup.admin.password", { n: PASSWORD_MIN })}
                 autoComplete="new-password"
-                className={inputCls}
               />
             </Section>
           )}
 
           {step === "google" && (
             <Section title={t("setup.google.title")} desc={t("setup.google.desc")}>
-              <input
+              <Input
+                className="w-full"
                 value={gid}
                 onChange={(e) => setGid(e.target.value)}
                 placeholder={t("setup.google.clientId")}
-                className={inputCls}
               />
-              <input
+              <Input
+                className="w-full"
                 value={gsecret}
                 onChange={(e) => setGsecret(e.target.value)}
                 placeholder={t("setup.google.clientSecret")}
-                className={inputCls}
               />
               <p className="text-xs text-muted">{t("setup.google.skipHint")}</p>
             </Section>
@@ -204,46 +204,46 @@ export default function SetupWizard() {
 
           {step === "smtp" && (
             <Section title={t("setup.smtp.title")} desc={t("setup.smtp.desc")}>
-              <input
+              <Input
+                className="w-full"
                 value={smtp.host}
                 onChange={(e) => setSmtp({ ...smtp, host: e.target.value })}
                 placeholder={t("setup.smtp.host")}
-                className={inputCls}
               />
               <div className="flex gap-2">
-                <input
+                <Input
+                  className="w-24"
                   value={smtp.port}
                   onChange={(e) => setSmtp({ ...smtp, port: e.target.value })}
                   placeholder={t("setup.smtp.port")}
-                  className={`${inputCls} w-24`}
                 />
-                <input
+                <Input
+                  className="w-full"
                   value={smtp.user}
                   onChange={(e) => setSmtp({ ...smtp, user: e.target.value })}
                   placeholder={t("setup.smtp.user")}
-                  className={inputCls}
                 />
               </div>
-              <input
+              <Input
+                className="w-full"
                 value={smtp.from}
                 onChange={(e) => setSmtp({ ...smtp, from: e.target.value })}
                 placeholder={t("setup.smtp.from")}
-                className={inputCls}
               />
-              <input
+              <Input
+                className="w-full"
                 type="password"
                 value={smtp.password}
                 onChange={(e) => setSmtp({ ...smtp, password: e.target.value })}
                 placeholder={t("setup.smtp.password")}
-                className={inputCls}
               />
               {smtp.host.trim() && (
                 <div className="flex items-center gap-2 pt-1">
-                  <input
+                  <Input
+                    className="w-full"
                     value={testTo}
                     onChange={(e) => setTestTo(e.target.value)}
                     placeholder={t("setup.smtp.testTo")}
-                    className={inputCls}
                   />
                   <Button
                     variant="glass"