feat(downloads): editor v2 — cut-list, join, aspect filmstrip + hover scrub

Rework VideoEditor around a segment cut-list: N draggable cut markers → segments, per-segment
keep/drop (eye toggle + dropped hatch), output = Separate files (one job per kept segment) or
Join into one (segments cut-list → one concatenated file). Per-segment numeric Start/End inputs.
Filmstrip fixed: aspect-correct tiles (no vertical squish) + YouTube-style hover-scrub thumbnail
from the sprite. EditSpec.segments type; editor v2 i18n (en/hu/de). Verified end-to-end in a real
browser (3-segment split, drop middle, join → 0:12 clip from a 0:19 source).

frontend/src/i18n/locales/en/editor.json

@@ -25,5 +25,21 @@
   "createN": "Create {{count}} clips",
   "created_one": "{{count}} clip added to your downloads",
   "created_other": "{{count}} clips added to your downloads",
-  "failed": "Couldn’t create the clip."
+  "failed": "Couldn’t create the clip.",
+  "splitHere": "Split here",
+  "output": {
+    "label": "Output",
+    "separate": "Separate files",
+    "join": "Join into one"
+  },
+  "segment": "Segment {{n}}",
+  "keep": "Keep",
+  "drop": "Drop",
+  "kept": "Kept",
+  "dropped": "Dropped",
+  "keptSeg": "Kept segment",
+  "droppedSeg": "Dropped segment",
+  "removeCut": "Remove cut",
+  "keptSummary": "{{n}} kept · {{dur}}",
+  "createJoin": "Create joined clip"
 }