feat: show reels in the profile grid, as Instagram does

The Posts tab filtered reels out, so the grid was not the archive — it
was the archive minus its videos. For `for.heejin` that hid 533 of 1225
posts; for `loonatheworld`, 1100 of 3813. On Instagram the grid holds
everything and the Reels tab is a filtered view of that same set.

Extract the tab logic to src/lib/post-tabs.ts so the reel heuristic is
testable outside the component, and add dedupePostCopies: the jd2 flow
crawls the profile URL and the /reels URL separately because the profile
page misses some reels, so the two overlap and a reel can land on disk
twice. Those are two posts with distinct directory-scoped ids, which the
grid would now render side by side; the reels-source copy wins so the
survivor is still recognised as a reel.

Deciding what *is* a reel stays a guess for most archives. Instagram
marks it with product_type ("clips" vs "feed" vs "igtv" — all three are
GraphVideo, and aspect ratio does not separate them), but only newer
Instaloader captures carry it: 1101 of gibiofficial's 5919 sidecars, and
only 2 marked clips. JDownloader archives carry none, so those still
fall back to treating a lone video as a reel.

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

package.json

@@ -1,7 +1,7 @@
 {
   "name": "instaarchive-viewer",
   "private": true,
-  "version": "1.6.2",
+  "version": "1.7.0",
   "type": "module",
   "scripts": {
     "dev": "vite --port=3000 --host=0.0.0.0",