chore: remove Electric SQL plumbing and infrastructure

Remove all Electric SQL client code, Docker service, env vars, CI build
args, install scripts, and documentation. Feature hooks that depend on
Electric are intentionally left in place to be rewritten with Rocicorp
Zero in subsequent commits.

Deleted:
- lib/electric/ (client.ts, context.ts, auth.ts, baseline.ts)
- ElectricProvider.tsx
- docker/scripts/init-electric-user.sh
- content/docs/how-to/electric-sql.mdx

Cleaned:
- package.json (4 @electric-sql/* deps)
- app/layout.tsx, UserDropdown.tsx, LayoutDataProvider.tsx
- docker-compose.yml, docker-compose.dev.yml
- Dockerfile, docker-entrypoint.js
- .env.example (frontend, docker, backend)
- CI workflows, install scripts, docs

docker/.env.example

@@ -35,7 +35,6 @@ EMBEDDING_MODEL=sentence-transformers/all-MiniLM-L6-v2
 
 # BACKEND_PORT=8929
 # FRONTEND_PORT=3929
-# ELECTRIC_PORT=5929
 # SEARXNG_PORT=8888
 # FLOWER_PORT=5555
 
@@ -58,7 +57,6 @@ EMBEDDING_MODEL=sentence-transformers/all-MiniLM-L6-v2
 # NEXT_PUBLIC_FASTAPI_BACKEND_AUTH_TYPE=LOCAL
 # NEXT_PUBLIC_ETL_SERVICE=DOCLING
 # NEXT_PUBLIC_DEPLOYMENT_MODE=self-hosted
-# NEXT_PUBLIC_ELECTRIC_AUTH_MODE=insecure
 
 # ------------------------------------------------------------------------------
 # Custom Domain / Reverse Proxy
@@ -71,7 +69,6 @@ EMBEDDING_MODEL=sentence-transformers/all-MiniLM-L6-v2
 # NEXT_FRONTEND_URL=https://app.yourdomain.com
 # BACKEND_URL=https://api.yourdomain.com
 # NEXT_PUBLIC_FASTAPI_BACKEND_URL=https://api.yourdomain.com
-# NEXT_PUBLIC_ELECTRIC_URL=https://electric.yourdomain.com
 
 
 # ------------------------------------------------------------------------------
@@ -101,19 +98,6 @@ EMBEDDING_MODEL=sentence-transformers/all-MiniLM-L6-v2
 # Supports TLS: rediss://:password@host:6380/0
 # REDIS_URL=redis://redis:6379/0
 
-# ------------------------------------------------------------------------------
-# Electric SQL (real-time sync credentials)
-# ------------------------------------------------------------------------------
-# These must match on the db, backend, and electric services.
-# Change for security; defaults work out of the box.
-
-# ELECTRIC_DB_USER=electric
-# ELECTRIC_DB_PASSWORD=electric_password
-# Full override for the Electric → Postgres connection URL.
-# Leave commented out to use the Docker-managed `db` container (default).
-# Uncomment and set `db` to `host.docker.internal` when pointing Electric at a local Postgres instance (e.g. Postgres.app on macOS):
-# ELECTRIC_DATABASE_URL=postgresql://electric:electric_password@db:5432/surfsense?sslmode=disable
-
 # ------------------------------------------------------------------------------
 # TTS & STT (Text-to-Speech / Speech-to-Text)
 # ------------------------------------------------------------------------------