rename(phase 1): CapaKraken → Nexus across code, UI, docs, CI

- @capakraken/* → @nexus/* across 12 packages (root + 11 workspaces),
  1551 import lines migrated via codemod
- User-visible brand strings renamed (emails, page titles, PWA
  manifest, mobile header, MFA backup-codes header, tooltips, signin
  page, invite page, weekly digest, install prompt)
- TOTP issuer "CapaKraken" → "Nexus" (existing secrets still valid;
  re-enrollment relabels them in users' authenticator apps)
- Function rename: assertCapaKrakenDbTarget → assertNexusDbTarget
- LocalStorage migration shim in apps/web/src/app/layout.tsx copies
  capakraken_* → nexus_* on first load (guarded by nexus_migrated_v1
  sentinel; runs once per browser, then never again)
- Service-worker cache name capakraken-v2 → nexus-v2 with one-time
  caches.delete('capakraken-v2') from the same shim
- Email-domain fixtures @capakraken.{dev,app} → @nexus.{dev,app} in
  seed data, e2e specs, SMTP default fallback
- Dockerfile.dev / Dockerfile.prod / all .github/workflows/*.yml
  pnpm --filter @capakraken/* → @nexus/*
- README, CLAUDE.md, LEARNINGS.md, all docs/*.md, .env.example,
  tooling/deploy/.env.production.example brand sweep

Phase 1 deliberately leaves untouched (handled in Phase 3 cutover):
- PostgreSQL DB name "capakraken" and POSTGRES_USER "capakraken"
- Volume names capakraken_pgdata etc.
- Compose project name "capakraken" / "capakraken-prod"
- db-target-guard default expectedDatabase
- env-var CAPAKRAKEN_EXPECTED_DB_NAME
- Container DNS names in docker-compose.ci.yml

Quality gates green: pnpm typecheck (7/7), pnpm test:unit (7/7),
pnpm lint (0 errors), check:exports/imports/architecture all pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.env.example

@@ -1,5 +1,5 @@
 # ─────────────────────────────────────────────────────────────────────────────
-# CapaKraken — environment variable reference
+# Nexus — environment variable reference
 #
 # Copy this file to .env and fill in the values before running the app.
 # Lines starting with # are comments. Lines with no value are optional.
@@ -12,7 +12,7 @@
 # REQUIRED — Public URL of the app (with scheme, no trailing slash).
 # Used in email links (invites, password reset) and as the Auth.js base URL.
 # Must use https:// in production.
-NEXTAUTH_URL=https://capakraken.example.com
+NEXTAUTH_URL=https://nexus.example.com
 
 # REQUIRED — Secret used to sign and encrypt JWTs and session cookies.
 # Generate one with: openssl rand -base64 32
@@ -65,7 +65,7 @@ REDIS_PASSWORD=
 # SMTP_PORT=587
 # SMTP_USER=no-reply@example.com
 # SMTP_PASSWORD=
-# SMTP_FROM=CapaKraken <no-reply@example.com>
+# SMTP_FROM=Nexus <no-reply@example.com>
 # SMTP_TLS=true     # "true" = SMTPS (port 465); "false" = STARTTLS or plain
 
 # ─── pgAdmin (dev / Docker Compose only) ─────────────────────────────────────
@@ -74,8 +74,8 @@ REDIS_PASSWORD=
 # Used as the password for the pgAdmin web UI (http://localhost:5050).
 PGADMIN_PASSWORD=
 
-# Email shown on the pgAdmin login screen (default: admin@capakraken.dev).
-# PGADMIN_EMAIL=admin@capakraken.dev
+# Email shown on the pgAdmin login screen (default: admin@nexus.dev).
+# PGADMIN_EMAIL=admin@nexus.dev
 
 # ─── Logging ─────────────────────────────────────────────────────────────────