Phase 2: character portraits → token icons (local + realtime)

- character.portrait + mapToken.image (data URLs, Dexie v10, additive).
- src/lib/img/resize.ts: center-crop + downscale helper (160px tokens / 256px
  portraits) keeping IndexedDB + wire payloads small.
- Portrait uploader on the character sheet; token icon uploader in the map token
  modal (falls back to the linked character's portrait). Palette PC entries show
  the portrait thumbnail.
- Tokens render the image clipped to the circle (HP ring + condition badge on top).
- Realtime: generalized the image channel to many images (map bg + token/portrait
  icons), deduped by content and resent on reconnect. Player tokens/party carry an
  imageId resolved from the session image cache; party panel shows portraits.
- Also: fix the encounter-picker dropdown text being clipped (drop fixed height).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/db/db.ts

@@ -100,6 +100,10 @@ export class TtrpgDatabase extends Dexie {
     // v9 — Phase 20: tokens gain optional combatantId (live HP from an encounter
     // combatant). Optional field — no backfill needed; existing rows parse fine.
     this.version(9).stores({});
+
+    // v10 — Phase 2: characters gain `portrait`, map tokens gain `image`
+    // (both optional data URLs). No backfill needed.
+    this.version(10).stores({});
   }
 }