feat(ui): overridable favicon/logo with branded default

Replace the ⚓ emoji with a real logo image used as the in-app brand
mark and the favicon. Default bundled public/logo.svg is the
HangmanLab mark recolored to the Foundry-Deck ember (#ff6a1a).
Override at deploy time via HARBORFORGE_LOGO_URL (injected into
runtime-config.js; getLogoUrl() + favicon swap), no rebuild needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -17,10 +17,14 @@ ENV FRONTEND_DEV_MODE=0
 # exists; /auth/config remains authoritative once the backend is up.
 ARG HARBORFORGE_OIDC_ONLY=false
 ENV HARBORFORGE_OIDC_ONLY=${HARBORFORGE_OIDC_ONLY}
+# Optional deploy-time branding override: a URL the SPA uses for the
+# logo + favicon. Empty → bundled /logo.svg default.
+ARG HARBORFORGE_LOGO_URL=
+ENV HARBORFORGE_LOGO_URL=${HARBORFORGE_LOGO_URL}
 EXPOSE 3000
 CMD ["sh", "-c", "\
   if [ \"$HARBORFORGE_OIDC_ONLY\" = \"true\" ]; then OO=true; else OO=false; fi; \
-  CFG=\"window.__HF_RUNTIME__={\\\"oidc_only\\\":$OO};\"; \
+  CFG=\"window.__HF_RUNTIME__={\\\"oidc_only\\\":$OO,\\\"logo_url\\\":\\\"$HARBORFORGE_LOGO_URL\\\"};\"; \
   mkdir -p public; printf '%s' \"$CFG\" > public/runtime-config.js; \
   [ -d dist ] && printf '%s' \"$CFG\" > dist/runtime-config.js; \
   if [ \"$FRONTEND_DEV_MODE\" = \"1\" ]; then npm run dev -- --host 0.0.0.0 --port 3000 --strictPort; else serve -s dist -l 3000; fi"]