feat: account enrichment using context.dev [UPM-27] (#13978)

## Account branding enrichment during signup

This PR does the following

### Replace Firecrawl with Context.dev

Switches the enterprise brand lookup from Firecrawl to Context.dev for
better data quality, built-in caching, and automatic filtering of
free/disposable email providers. The service interface changes from URL
to email input to match Context.dev's email endpoint. OSS still falls
back to basic HTML scraping with a normalized output shape across both
paths.

The enterprise path intentionally does not fall back to HTML scraping on
failure — speed matters more than completeness. We want the user on the
editable onboarding form fast, and a slow fallback scrape is worse than
letting them fill it in.

Requires `CONTEXT_DEV_API_KEY` in Super Admin → App Config. Without it,
falls back to OSS HTML scraping.

### Add job to enrich account details

After account creation, `Account::BrandingEnrichmentJob` looks up the
signup email and pre-fills the account name, colors, logos, social
links, and industry into `custom_attributes['brand_info']`.

The job signals completion via a short-lived Redis key (30s TTL) + an
ActionCable broadcast (`account.enrichment_completed`). The Redis key
lets the frontend distinguish "still running" from "finished with no
results."

lib/redis/redis_keys.rb

@@ -50,6 +50,9 @@ module Redis::RedisKeys
   ASSIGNMENT_KEY = 'ASSIGNMENT::%<inbox_id>d::AGENT::%<agent_id>d::CONVERSATION::%<conversation_id>d'.freeze
   ASSIGNMENT_KEY_PATTERN = 'ASSIGNMENT::%<inbox_id>d::AGENT::%<agent_id>d::*'.freeze
 
+  ## Account Onboarding
+  ACCOUNT_ONBOARDING_ENRICHMENT = 'ONBOARDING_ENRICHMENT::%<account_id>d'.freeze
+
   ## Account Email Rate Limiting
   ACCOUNT_OUTBOUND_EMAIL_COUNT_KEY = 'OUTBOUND_EMAIL_COUNT::%<account_id>d::%<date>s'.freeze
 end