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/scripts/init-electric-user.sh

@@ -1,38 +0,0 @@
-#!/bin/sh
-# Creates the Electric SQL replication user on first DB initialization.
-# Idempotent — safe to run alongside Alembic migration 66.
-
-set -e
-
-ELECTRIC_DB_USER="${ELECTRIC_DB_USER:-electric}"
-ELECTRIC_DB_PASSWORD="${ELECTRIC_DB_PASSWORD:-electric_password}"
-
-echo "Creating Electric SQL replication user: $ELECTRIC_DB_USER"
-
-psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
-    DO \$\$
-    BEGIN
-        IF NOT EXISTS (SELECT FROM pg_user WHERE usename = '$ELECTRIC_DB_USER') THEN
-            CREATE USER $ELECTRIC_DB_USER WITH REPLICATION PASSWORD '$ELECTRIC_DB_PASSWORD';
-        END IF;
-    END
-    \$\$;
-
-    GRANT CONNECT ON DATABASE $POSTGRES_DB TO $ELECTRIC_DB_USER;
-    GRANT CREATE ON DATABASE $POSTGRES_DB TO $ELECTRIC_DB_USER;
-    GRANT USAGE ON SCHEMA public TO $ELECTRIC_DB_USER;
-    GRANT SELECT ON ALL TABLES IN SCHEMA public TO $ELECTRIC_DB_USER;
-    GRANT SELECT ON ALL SEQUENCES IN SCHEMA public TO $ELECTRIC_DB_USER;
-    ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO $ELECTRIC_DB_USER;
-    ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON SEQUENCES TO $ELECTRIC_DB_USER;
-
-    DO \$\$
-    BEGIN
-        IF NOT EXISTS (SELECT FROM pg_publication WHERE pubname = 'electric_publication_default') THEN
-            CREATE PUBLICATION electric_publication_default;
-        END IF;
-    END
-    \$\$;
-EOSQL
-
-echo "Electric SQL user '$ELECTRIC_DB_USER' and publication created successfully"

docker/scripts/install.ps1

@@ -109,7 +109,6 @@ $Files = @(
     @{ Src = "docker/docker-compose.yml";                Dest = "docker-compose.yml" }
     @{ Src = "docker/.env.example";                      Dest = ".env.example" }
     @{ Src = "docker/postgresql.conf";                   Dest = "postgresql.conf" }
-    @{ Src = "docker/scripts/init-electric-user.sh";     Dest = "scripts/init-electric-user.sh" }
     @{ Src = "docker/scripts/migrate-database.ps1";      Dest = "scripts/migrate-database.ps1" }
     @{ Src = "docker/searxng/settings.yml";              Dest = "searxng/settings.yml" }
     @{ Src = "docker/searxng/limiter.toml";              Dest = "searxng/limiter.toml" }

docker/scripts/install.sh

@@ -108,7 +108,6 @@ FILES=(
     "docker/docker-compose.yml:docker-compose.yml"
     "docker/.env.example:.env.example"
     "docker/postgresql.conf:postgresql.conf"
-    "docker/scripts/init-electric-user.sh:scripts/init-electric-user.sh"
     "docker/scripts/migrate-database.sh:scripts/migrate-database.sh"
     "docker/searxng/settings.yml:searxng/settings.yml"
     "docker/searxng/limiter.toml:searxng/limiter.toml"
@@ -122,7 +121,6 @@ for entry in "${FILES[@]}"; do
         || error "Failed to download ${dest}. Check your internet connection and try again."
 done
 
-chmod +x "${INSTALL_DIR}/scripts/init-electric-user.sh"
 chmod +x "${INSTALL_DIR}/scripts/migrate-database.sh"
 success "All files downloaded to ${INSTALL_DIR}/"