refactor(webapp): remove emoji web app logo option

Drop the emoji-logo feature (and its font picker) from the Web App. Only
an uploaded/linked image logo and favicon remain; when no logo is set,
the default project logo is shown. Existing emoji-logo overrides are
ignored — the keys are gone from the manifest, so the override service
skips them and the app falls back to the default logo.

- Remove WEBAPP_LOGO_USE_EMOJI / WEBAPP_LOGO_EMOJI / WEBAPP_LOGO_EMOJI_FONT
  settings, validators, manifest entries and override/runtime plumbing.
- Strip the animated-emoji fetch/cache subsystem, the /webapp-emoji route
  and emoji branches from logo/favicon resolution; leftover emoji cache
  files are now purged on appearance save.
- Simplify BrandMark to an image-only component and drop the emoji UI
  from the admin Appearance section.
- Regenerate the demo settings manifest and clean docs, locales, nginx
  and demo data of emoji-logo references.

backend/bot/app/web/admin_api_impl/themes.py

@@ -136,10 +136,6 @@ def _favicon_digest(url: str) -> Optional[str]:
     return match.group(1) if match else None
 
 
-def _emoji_to_codepoints(value: str) -> str:
-    return "_".join(f"{ord(char):x}" for char in str(value or "").strip())
-
-
 def prune_unused_appearance_assets(settings: Settings) -> None:
     keep_logos = {
         filename
@@ -156,15 +152,6 @@ def prune_unused_appearance_assets(settings: Settings) -> None:
         ]
         if digest
     }
-    keep_emoji_prefixes = set()
-    if (
-        getattr(settings, "WEBAPP_LOGO_USE_EMOJI", False)
-        and str(getattr(settings, "WEBAPP_LOGO_EMOJI_FONT", "") or "").strip()
-        == "noto-color-animated"
-    ):
-        codepoints = _emoji_to_codepoints(getattr(settings, "WEBAPP_LOGO_EMOJI", ""))
-        if codepoints:
-            keep_emoji_prefixes.add(f"{codepoints}.512.")
 
     for path in WEBAPP_UPLOADED_LOGO_DIR.glob("logo-*"):
         if path.is_file() and path.name not in keep_logos:
@@ -184,10 +171,9 @@ def prune_unused_appearance_assets(settings: Settings) -> None:
             except OSError:
                 logger.warning("Failed to remove unused webapp favicon set %s", path, exc_info=True)
 
+    # Emoji logos were removed; purge any leftover animated-emoji cache files.
     for path in WEBAPP_EMOJI_CACHE_DIR.glob("*.512.*"):
-        if path.is_file() and not any(
-            path.name.startswith(prefix) for prefix in keep_emoji_prefixes
-        ):
+        if path.is_file():
             try:
                 path.unlink()
             except OSError:
@@ -389,7 +375,6 @@ async def admin_appearance_logo_upload_route(request: web.Request) -> web.Respon
         request,
         {
             "WEBAPP_LOGO_URL": logo_url,
-            "WEBAPP_LOGO_USE_EMOJI": False,
             **(
                 {"WEBAPP_LOGO_FAVICON_URL": favicon_payload["favicon_url"]}
                 if favicon_payload.get("favicon_url")

backend/bot/app/web/admin_api_impl/webapp_runtime.py

@@ -13,9 +13,6 @@ WEBAPP_APPEARANCE_SETTING_KEYS = frozenset(
     {
         "WEBAPP_TITLE",
         "WEBAPP_LOGO_URL",
-        "WEBAPP_LOGO_USE_EMOJI",
-        "WEBAPP_LOGO_EMOJI",
-        "WEBAPP_LOGO_EMOJI_FONT",
         "WEBAPP_FAVICON_URL",
         "WEBAPP_FAVICON_USE_CUSTOM",
         "WEBAPP_LOGO_FAVICON_URL",