feat(review): flag handles in the review player (metadata only)

Renders run 8 frames past the cut at each end. Directors were flagging
glitches in unfixed handles as shot problems, so the player now marks
them — without trimming or burning anything into the EXRs/MOV/MP4.

- Version.handleHead/handleTail/pictureStartFrame, Export.handleHead/
  handleTail; migration backfills pipeline exports and their preview
  versions from the manifest's handleFrames (else 8)
- AE panel: "Includes handles [8] frames each end" -> manifest.review;
  older manifests fall back to source.handleFrames
- finalize copies handles onto the Version; worker 1.6.4 reports the
  head slate length (pictureStartSeconds), else the player infers it
  as MP4 frames - EXR frameCount
- Player: hatched HANDLE / SLATE regions and cut marks on the timeline,
  "HEAD/TAIL HANDLE · NOT IN EDIT" overlay on handle frames, HANDLE badge
  on notes, "Edit range only" toggle (default on in the client portal)
- Staff Handles editor on the review page for manual uploads/corrections

Also fixes two player bugs found while testing: timeToFrame floored
float error (every seek landed a frame early), and J/reverse never ran
(the keyboard effect's cleanup stopped it on the next render).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

components/comments/CommentPanel.tsx

@@ -10,6 +10,7 @@ import { Badge } from "@/components/ui/badge";
 import { cn } from "@/lib/utils";
 import { getInitials, formatRelativeDate } from "@/lib/utils";
 import { frameToTimecode } from "@/lib/frame-utils";
+import { HandleBadge } from "@/components/player/HandleBadge";
 import {
   CheckCircle2,
   Circle,
@@ -151,6 +152,7 @@ export function CommentPanel({
             <span className="text-xs text-muted-foreground">
               {frameToTimecode(activeCommentFrame, fps)}
             </span>
+            <HandleBadge frame={activeCommentFrame} />
           </div>
           <Textarea
             ref={inputRef}
@@ -348,6 +350,7 @@ function CommentThread({
               >
                 F{String(comment.frameNumber).padStart(4, "0")}
               </button>
+              <HandleBadge frame={comment.frameNumber} />
               <span className="text-xs text-muted-foreground ml-auto">
                 {formatRelativeDate(comment.createdAt)}
               </span>