chore: replace TurboStarter brand references in env templates + docs

- PRODUCT_NAME default: TurboStarter → claudemesh (.env.example, .env.local)
- SEED_EMAIL default: me@turbostarter.dev → dev@example.com
- README dev accounts table: reflect new seed email format
- DEPLOY.md: fix stale SEED_EMAIL reference

Keeps DB user as turbostarter per docker-compose.yml default; retains
TurboStarter attribution link in README Contributing section (legit
credit for the template this repo is built on).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.env.example

@@ -9,7 +9,7 @@
 DATABASE_URL="postgresql://turbostarter:turbostarter@localhost:5432/core"
 
 # The name of the product. This is used in various places across the apps.
-PRODUCT_NAME="TurboStarter"
+PRODUCT_NAME="claudemesh"
 
 # The url of the web app. Used mostly to link between apps.
 URL="http://localhost:3000"