brand: rename product to "Read the Markets" (read.markets)

The product is now "Read the Markets" served at https://read.markets,
with the app at https://app.read.markets. "Cassandra" survives only as
the in-product AI persona (system prompt + "Ask Cassandra" chat label).

Centralised the brand in app/branding.py: BRAND_NAME, BRAND_SHORT,
DOMAIN, SITE_URL, APP_URL, EMAIL_FROM_DEFAULT. Jinja templates pull
{{ BRAND_NAME }} via globals registered in templates_env.py; Python
code reads branding.BRAND_NAME directly. The future-rename surface
is now a one-liner.

Updated: FastAPI app title, every page title (dashboard, news, log,
settings, upload, login, verify), header brand div, auth-card brands,
OTP email subject + HTML + plain-text bodies (incl. uppercase header
tag), OpenRouter X-Title + HTTP-Referer attribution headers, README.
Email tests now assert against branding.BRAND_NAME rather than the
literal string.

Internal identifiers deliberately kept on the legacy "cassandra" name
to avoid invalidating live sessions / advisory locks / configs:
cookies (cassandra_session, cassandra_pending) + itsdangerous salts,
MariaDB GET_LOCK keys, CASSANDRA_TOKEN env var, cassandra.css filename,
pyproject package name, localStorage prefs, outbound User-Agent strings.

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

app/main.py

@@ -13,6 +13,7 @@ from fastapi import FastAPI
 from fastapi.middleware.gzip import GZipMiddleware
 from fastapi.staticfiles import StaticFiles
 
+from app import branding
 from app.config import get_settings
 from app.db import get_session_factory
 from app.logging import configure_logging, get_logger
@@ -56,7 +57,7 @@ async def lifespan(app: FastAPI):
 
 
 app = FastAPI(
-    title="Cassandra",
+    title=branding.BRAND_NAME,
     description="Macro-strategy dashboard",
     version="0.1.0",
     lifespan=lifespan,