Fall back instead of rendering broken roster images (#389)

[avandenberghe]

Closes #389.

Every roster image URL was built straight from a DB value with no existence check, so a game plugin missing one asset rendered a broken image. That is the shared root cause behind the per-plugin icon tickets (bbguildeq#7, bbguildeq2#7, bbguildffxiv#4, bbguildgw2#7, bbguildlineage2#3/#7, bbguildlotro#3, bbguildswtor#3), and the only fix that scales to bbguildlineage2's 110 missing roster portraits.

What changed

• class_image_candidates() — roster art → detail icon → the game's <prefix>_unknown icon in either directory
• character_image_candidates() — the character's class/race image, then the same-directory unknown icon
• resolve_game_image() — first candidate that exists on disk, re-anchoring the web path at its ext/ segment the way resolve_portrait_with_fallback() already does; '' when none exist
• roster_center.html guards all four <img> sites, so an unresolved image omits the tag instead of emitting an empty src
• DB-sourced names are reduced to basename(), so a crafted imagename cannot walk out of the images directory

Tests

13 new tests in tests/portal/roster_image_fallback_test.php cover candidate ordering, the traversal strip, and each fallback step. They resolve against core's own images/{roster_classes,class_images}/custom_*.png — no game plugin involved, so they hold in CI where none are installed.

Full core unit suite: 115 tests, 306 assertions, green.

🤖 Generated with Claude Code

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