feat(docker): bundle PostgreSQL into the unified container

Transition from a multi-service architecture to an all-in-one container
by bundling PostgreSQL directly within the Docker image. This simplifies
deployment, especially for environments like CasaOS, by removing the
need for an external database service.

- Update Dockerfile to install and configure PostgreSQL
- Implement database initialization logic in docker-entrypoint.sh
- Update .env.example to reflect auto-generation of credentials
- Simplify docker-compose.yml to a single service
- Update README.md with new deployment instructions and architecture details

docker-entrypoint.sh

@@ -1,24 +1,86 @@
 #!/bin/sh
 
-# Unified entrypoint for Trackeep
-# Starts both backend and nginx in one container
+# All-in-one entrypoint for Trackeep
+# Initializes and starts PostgreSQL, then backend + nginx
 
 set -e
 
-# Backend configuration
+PGDATA=${PGDATA:-/var/lib/postgresql/data}
+
+# Auto-generate DB_PASSWORD if not provided
+if [ -z "$DB_PASSWORD" ]; then
+    DB_PASSWORD=$(tr -dc 'a-zA-Z0-9' < /dev/urandom | head -c 32)
+    echo "========================================"
+    echo "WARNING: DB_PASSWORD was not set."
+    echo "Auto-generated password: $DB_PASSWORD"
+    echo "Set DB_PASSWORD explicitly to keep it stable across restarts."
+    echo "========================================"
+fi
+
+DB_USER=${DB_USER:-trackeep}
+DB_NAME=${DB_NAME:-trackeep}
+
+# Initialize PostgreSQL if data directory is empty
+if [ ! -f "$PGDATA/PG_VERSION" ]; then
+    echo "Initializing PostgreSQL database cluster..."
+    su -s /bin/sh postgres -c "initdb -D $PGDATA --auth-local=trust --auth-host=md5"
+
+    # Allow local TCP connections
+    echo "host all all 127.0.0.1/32 md5" >> "$PGDATA/pg_hba.conf"
+    echo "host all all ::1/128 md5"     >> "$PGDATA/pg_hba.conf"
+
+    # Start postgres temporarily to create user and database
+    su -s /bin/sh postgres -c "pg_ctl -D $PGDATA -l /var/log/postgresql/server.log start"
+
+    # Wait until postgres accepts connections
+    echo "Waiting for PostgreSQL to accept connections..."
+    for i in $(seq 1 30); do
+        if su -s /bin/sh postgres -c "pg_isready -q"; then
+            break
+        fi
+        sleep 1
+    done
+
+    # Create role and database
+    su -s /bin/sh postgres -c "psql -c \"CREATE USER \\\"$DB_USER\\\" WITH PASSWORD '$DB_PASSWORD';\""
+    su -s /bin/sh postgres -c "psql -c \"CREATE DATABASE \\\"$DB_NAME\\\" OWNER \\\"$DB_USER\\\";\""
+
+    su -s /bin/sh postgres -c "pg_ctl -D $PGDATA stop"
+    echo "PostgreSQL initialized."
+fi
+
+# Start PostgreSQL
+echo "Starting PostgreSQL..."
+su -s /bin/sh postgres -c "pg_ctl -D $PGDATA -l /var/log/postgresql/server.log start"
+
+# Wait for PostgreSQL to be ready
+echo "Waiting for PostgreSQL to be ready..."
+for i in $(seq 1 30); do
+    if su -s /bin/sh postgres -c "pg_isready -q"; then
+        echo "PostgreSQL is ready."
+        break
+    fi
+    echo "Waiting for PostgreSQL... ($i/30)"
+    sleep 1
+done
+
+# Backend connects to the bundled local PostgreSQL
 export BACKEND_PORT=8081
-export DB_HOST=${DB_HOST:-postgres}
-export DB_PORT=${DB_PORT:-5432}
-export DB_NAME=${DB_NAME:-trackeep}
-export DB_USER=${DB_USER:-trackeep}
-export DB_PASSWORD=${DB_PASSWORD}
-export JWT_SECRET=${JWT_SECRET}
+export DB_HOST=localhost
+export DB_PORT=5432
+export DB_NAME="$DB_NAME"
+export DB_USER="$DB_USER"
+export DB_PASSWORD="$DB_PASSWORD"
+export DB_SSL_MODE=disable
+export JWT_SECRET=${JWT_SECRET:-}
 export GIN_MODE=${GIN_MODE:-release}
+export CORS_ALLOWED_ORIGINS=${CORS_ALLOWED_ORIGINS:-*}
 
 # Start backend in background
 cd /app
 echo "Starting Trackeep backend on port ${BACKEND_PORT}..."
 ./main &
+BACKEND_PID=$!
 
 # Wait for backend to be ready
 echo "Waiting for backend to be ready..."
@@ -31,6 +93,6 @@ for i in $(seq 1 30); do
     sleep 2
 done
 
-# Start nginx
-echo "Starting nginx..."
+# Start nginx in foreground (keeps container alive)
+echo "Starting nginx on port 8080..."
 nginx -g "daemon off;"