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/Welcome.tsx

@@ -31,12 +31,12 @@ import LanguageSwitcher from "./LanguageSwitcher";
 import { Button } from "./ui/Button";
 import { trapTab, useDialogChrome } from "./ui/dialogFocus";
 import { anyBlockingLayerAbove, isTopmost, pushLayer, removeLayer } from "../lib/layerStack";
-import { inputCls } from "./ui/form";
 import { entryHash, entrySearch } from "../lib/entryUrl";
 import type { VerifyEntry } from "../lib/useVerifyEntry";
 import { MODE_URL, type Mode } from "./welcomeMode";
 import { IconButton } from "./ui/IconButton";
 import { Pressable } from "./ui/Pressable";
+import { Input } from "./ui/Input";
 
 const EMAIL_RE = /^[^@\s]+@[^@\s]+\.[^@\s]+$/;
 const PASSWORD_MIN = 10;
@@ -660,18 +660,19 @@ function AuthCard({ verify }: { verify: VerifyEntry }) {
         <>
           <form onSubmit={onSubmit} className="flex flex-col gap-3 mt-3">
             {mode !== "reset" && (
-              <input
+              <Input
+                className="w-full"
                 type="email"
                 autoComplete="email"
                 required
                 value={email}
                 onChange={(e) => setEmail(e.target.value)}
                 placeholder={t("welcome.auth.email")}
-                className={inputCls}
               />
             )}
             {mode !== "forgot" && mode !== "resend" && (
-              <input
+              <Input
+                className="w-full"
                 type="password"
                 autoComplete={mode === "signin" ? "current-password" : "new-password"}
                 required
@@ -682,7 +683,6 @@ function AuthCard({ verify }: { verify: VerifyEntry }) {
                     ? t("welcome.auth.newPassword", { min: PASSWORD_MIN })
                     : t("welcome.auth.password")
                 }
-                className={inputCls}
               />
             )}
             {error && (
@@ -769,12 +769,12 @@ function AuthCard({ verify }: { verify: VerifyEntry }) {
                 <form onSubmit={onDemo} className="mt-2 flex flex-col gap-2">
                   <p className="text-2xs text-muted">{t("welcome.auth.demoHint")}</p>
                   <div className="flex gap-2">
-                    <input
+                    <Input
+                      className="w-full"
                       type="email"
                       value={demoEmail}
                       onChange={(e) => setDemoEmail(e.target.value)}
                       placeholder={t("welcome.auth.demoEmail")}
-                      className={inputCls}
                     />
                     <Button type="submit" variant="outline" size="lg" disabled={demoBusy}>
                       {demoBusy ? t("welcome.auth.working") : t("welcome.auth.demoEnter")}