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>

scripts/export-dev-seed.mjs

@@ -129,7 +129,7 @@ UPDATE webhooks SET secret = NULL;
 
 // ── Add header ────────────────────────────────────────────────────────────────
 
-const header = `-- CapaKraken dev seed — exported ${new Date().toISOString()}
+const header = `-- Nexus dev seed — exported ${new Date().toISOString()}
 -- Source: ${DB_USER}@${host}:${DB_PORT}/${DB_NAME}
 --
 -- Excluded tables:

scripts/prisma-with-env.mjs

@@ -27,12 +27,12 @@ if (shouldGuardPrismaCommand(prismaArgs)) {
   } catch (error) {
     console.error(error instanceof Error ? error.message : String(error));
     console.error("Refusing to run Prisma against an unexpected database target.");
-    console.error("Use the repo env files for CapaKraken, or set CAPAKRAKEN_EXPECTED_DB_NAME explicitly if you intentionally target another database.");
+    console.error("Use the repo env files for Nexus, or set CAPAKRAKEN_EXPECTED_DB_NAME explicitly if you intentionally target another database.");
     process.exit(1);
   }
 }
 
-const result = spawnSync("pnpm", ["--filter", "@capakraken/db", "exec", "prisma", ...prismaArgs], {
+const result = spawnSync("pnpm", ["--filter", "@nexus/db", "exec", "prisma", ...prismaArgs], {
   stdio: "inherit",
   env: process.env,
   cwd: workspaceRoot,