anki decks: add multiple-choice shapes variant; add real element photos to periodic table

shapes_mc (tools/anki-deck-visual.py) is the same shape images as
"shapes" but multiple choice instead of type-the-name, matching the
plain-text A/B/C/D pattern anki-deck-periodic.py's "category" deck
already uses (no clickable UI, since that needs a desktop-only Anki
add-on and breaks on AnkiDroid/AnkiMobile).

periodic prehs/hs (tools/anki-deck-periodic.py) now show each element's
real sample photo alongside every card, fetched once from Wikipedia's
own MediaWiki pageimages API and cached under tools/periodic_images/ —
the one part of this tooling that needs internet access at generation
time; --no-images restores the old text-only cards. Elements 100
(Fermium) through 118 (Oganesson) are excluded, since none has ever
existed in a photographable quantity — every fetch is otherwise
per-element and non-fatal, with progress printed so failures are visible.

This fetch logic could not be exercised against the real Wikipedia API
from this sandbox (no route to en.wikipedia.org here) — --dry-run-tts
now also substitutes a placeholder image so the pipeline is at least
structurally tested end to end. Real-network behavior needs verifying
on an actual run.

Added tools/*.apkg, tools/media_*/, tools/periodic_images/, and
tools/__pycache__/ to .gitignore — all generated/cached locally, never
meant to be committed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014DyceEVVeQ33EeS6C1PDv5

.gitignore

@@ -1,2 +1,10 @@
 # Vanilla Tweaks ZIP files placed for automatic install — never commit these
 extras/datapacks/*.zip
+
+# tools/anki-deck-*.py output and caches — generated locally, regenerable,
+# never meant to be committed (periodic_images/ especially: fetched
+# element photos, not source)
+tools/*.apkg
+tools/media_*/
+tools/periodic_images/
+tools/__pycache__/