revert(player): drop the transform-scale HD hack (didn't beat YouTube's cap)

Confirmed on prod: rendering the iframe at 1920x1080 logical and CSS transform:
scale()-ing it down does NOT lift YouTube's quality cap — the embed stays ~360p in
the windowed player and manual HD still snaps back; only true fullscreen unlocks
1080p (which then persists for the session). YouTube caps by the on-screen size, not
the iframe's window.innerWidth, so the transform only shrank YouTube's native
controls for no benefit. Restore the plain 100%/100% mount.

Kept: scroll-anywhere volume (works), the native-menu-yield fix, max-w-6xl, and the
harmless vq=hd1080 hint.

frontend/src/components/PlayerModal.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useLayoutEffect, useRef, useState } from "react";
+import { useEffect, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { createPortal } from "react-dom";
 import { useQuery, useQueryClient } from "@tanstack/react-query";
@@ -20,15 +20,6 @@ import { useBackToClose } from "../lib/history";
 // How close to the end (seconds) counts as "finished" → auto-mark watched.
 const FINISH_MARGIN = 10;
 
-// Fixed logical size the player iframe is rendered at, then CSS-scaled down to fit the (smaller)
-// on-screen stage. YouTube caps an embed's max quality to the player's OWN inner viewport size, so
-// a physically small player is stuck at ~360p even if you pick 1080p manually — it snaps back. A
-// CSS `transform: scale()` shrinks the visual box WITHOUT changing the iframe's window.innerWidth,
-// so YouTube keeps seeing a 1920×1080 viewport and allows 1080p while we display it small. (Actual
-// quality is still bandwidth-gated by YouTube, but manual HD selection now sticks.)
-const PLAYER_BASE_W = 1920;
-const PLAYER_BASE_H = 1080;
-
 // Persistent playback settings (stored in users.preferences). Auto-advance = what plays when a
 // video ends; loop = whether it repeats the current video ("one"), wraps the list at its ends
 // ("all"), or neither ("off"). Both apply to any queued player (feed or playlist).
@@ -133,8 +124,6 @@ export default function PlayerModal({
   // modal adjusts volume (not just the small player area).
   const dialogRef = useRef<HTMLDivElement | null>(null);
   const volTimerRef = useRef<number | undefined>(undefined);
-  // CSS scale that fits the 1920×1080 logical player onto the actual stage (see PLAYER_BASE_* above).
-  const [playerScale, setPlayerScale] = useState(0);
   // Volume level to flash in the on-player overlay (null = hidden). Auto-fades after a moment.
   const [volumeUi, setVolumeUi] = useState<number | null>(null);
   // When the user interacts with YouTube's own controls (gear/seek/CC), focus moves into the
@@ -416,25 +405,6 @@ export default function PlayerModal({
     return () => el.removeEventListener("wheel", onWheel);
   }, []);
 
-  // Keep the 1920×1080 logical player scaled to exactly fit the on-screen stage (windowed AND
-  // fullscreen). Measured before paint so the player never flashes at the wrong size.
-  useLayoutEffect(() => {
-    const stage = stageRef.current;
-    if (!stage) return;
-    const update = () => {
-      const w = stage.clientWidth;
-      if (w > 0) setPlayerScale(w / PLAYER_BASE_W);
-    };
-    update();
-    const ro = new ResizeObserver(update);
-    ro.observe(stage);
-    document.addEventListener("fullscreenchange", update);
-    return () => {
-      ro.disconnect();
-      document.removeEventListener("fullscreenchange", update);
-    };
-  }, []);
-
   // Yield the interaction overlay to YouTube's native UI. Clicking a native control (gear / seek
   // bar / CC) moves focus into the player iframe — the only cross-origin signal we get. While the
   // iframe holds focus we drop the overlay's pointer-events so the (arbitrarily tall) settings
@@ -517,9 +487,11 @@ export default function PlayerModal({
           origin: window.location.origin,
           playsinline: 1,
           // Best-effort HD hint. The IFrame API's setPlaybackQuality/suggestedQuality are hard no-ops
-          // now (YouTube removed them), but the undocumented `vq` URL param is still honoured for many
+          // now (YouTube removed them), and the undocumented `vq` URL param is only occasionally
-          // videos and is harmless otherwise. The real quality lever is the player's rendered size
+          // honoured — kept because it's harmless. NOTE: YouTube hard-caps an embed's max quality by
-          // (see max-w-6xl below) — YouTube's ABR targets a resolution to match the pixel box.
+          // the player's on-screen size; a windowed embed is stuck ~360p and only true fullscreen
+          // lifts the cap (after which the higher pick persists for the session). We can't beat that
+          // programmatically — a CSS transform-scale trick was tried and does NOT fool the cap.
           vq: "hd1080",
         },
         events: {
@@ -609,15 +581,9 @@ export default function PlayerModal({
           ref={stageRef}
           className="player-stage relative aspect-video w-full bg-black rounded-t-2xl overflow-hidden"
         >
-          {/* The player rendered at a fixed 1920×1080 logical size, then CSS-scaled down to fit the
+          {/* Hide the iframe entirely on error so YouTube's own error screen can't bleed
-              stage — this is what unlocks 1080p in the small windowed player (see PLAYER_BASE_*).
+              through our overlay. */}
-              Hide the iframe entirely on error so YouTube's own error screen can't bleed through. */}
+          <div ref={mountRef} className={`w-full h-full ${playerError != null ? "invisible" : ""}`} />
-          <div
-            className="absolute top-0 left-0 origin-top-left"
-            style={{ width: PLAYER_BASE_W, height: PLAYER_BASE_H, transform: `scale(${playerScale})` }}
-          >
-            <div ref={mountRef} className={`w-full h-full ${playerError != null ? "invisible" : ""}`} />
-          </div>
           {/* Interaction layer over the CENTRE of the video: catches click (play/pause) and stops
               the iframe stealing keyboard focus. It deliberately leaves the top AND bottom edges
               uncovered so YouTube's native controls — the top-right cluster (volume / CC / settings)