feat(db): add postgres setup and multi-tenant config

src/main/java/com/caspos/config/tenant/SchemaBasedMultiTenantConnectionProvider.java

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+package com.caspos.config.tenant;
+
+import org.hibernate.engine.jdbc.connections.spi.MultiTenantConnectionProvider;
+import org.springframework.stereotype.Component;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.SQLException;
+
+@Component
+public class SchemaBasedMultiTenantConnectionProvider implements MultiTenantConnectionProvider<String> {
+
+    private final DataSource dataSource;
+
+    public SchemaBasedMultiTenantConnectionProvider(DataSource dataSource) {
+        this.dataSource = dataSource;
+    }
+
+    @Override
+    public Connection getAnyConnection() throws SQLException {
+        return dataSource.getConnection();
+    }
+
+    @Override
+    public void releaseAnyConnection(Connection connection) throws SQLException {
+        connection.close();
+    }
+
+    @Override
+    public Connection getConnection(String tenantIdentifier) throws SQLException {
+        final Connection connection = getAnyConnection();
+        connection.setSchema(tenantIdentifier);
+        return connection;
+    }
+
+    @Override
+    public void releaseConnection(String tenantIdentifier, Connection connection) throws SQLException {
+        try {
+            connection.setSchema("public");
+        } finally {
+            releaseAnyConnection(connection);
+        }
+    }
+
+    @Override
+    public boolean supportsAggressiveRelease() {
+        return true;
+    }
+
+    @Override
+    public boolean isUnwrappableAs(Class<?> unwrapType) {
+        return MultiTenantConnectionProvider.class.isAssignableFrom(unwrapType);
+    }
+
+    @Override
+    public <T> T unwrap(Class<T> unwrapType) {
+        if (isUnwrappableAs(unwrapType)) {
+            return unwrapType.cast(this);
+        }
+        throw new IllegalArgumentException("Can't unwrap to " + unwrapType.getName());
+    }
+}

src/main/java/com/caspos/config/tenant/TenantContext.java

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+package com.caspos.config.tenant;
+
+public final class TenantContext {
+
+    private static final String DEFAULT_TENANT = "public";
+    private static final ThreadLocal<String> CURRENT_TENANT = ThreadLocal.withInitial(() -> DEFAULT_TENANT);
+
+    private TenantContext() {}
+
+    public static String getCurrentTenant() {
+        return CURRENT_TENANT.get();
+    }
+
+    public static void setCurrentTenant(String tenantSchema) {
+        if (tenantSchema == null || tenantSchema.isBlank()) {
+            CURRENT_TENANT.set(DEFAULT_TENANT);
+        } else {
+            CURRENT_TENANT.set(tenantSchema);
+        }
+    }
+
+    public static void clear() {
+        CURRENT_TENANT.set(DEFAULT_TENANT);
+    }
+}

src/main/java/com/caspos/config/tenant/TenantIdentifierResolver.java

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+package com.caspos.config.tenant;
+
+import org.hibernate.context.spi.CurrentTenantIdentifierResolver;
+import org.springframework.stereotype.Component;
+
+@Component
+public class TenantIdentifierResolver implements CurrentTenantIdentifierResolver<String> {
+
+    @Override
+    public String resolveCurrentTenantIdentifier() {
+        String tenant = TenantContext.getCurrentTenant();
+        return (tenant != null && !tenant.isBlank()) ? tenant : "public";
+    }
+
+    @Override
+    public boolean validateExistingCurrentSessions() {
+        return true;
+    }
+}

src/main/resources/application.yml

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+spring:
+  datasource:
+    url: jdbc:postgresql://${POSTGRES_HOST:localhost}:${POSTGRES_PORT:5432}/${POSTGRES_DB:smartseat_db}
+    username: ${POSTGRES_USER:postgres_admin}
+    password: ${POSTGRES_PASSWORD:change_me_super_secret_admin_password}
+    driver-class-name: org.postgresql.Driver
+    hikari:
+      maximum-pool-size: 20
+      minimum-idle: 5
+      idle-timeout: 300000
+      connection-timeout: 20000
+      max-lifetime: 1200000
+      leak-detection-threshold: 5000
+      pool-name: CasposHikariCP
+
+  jpa:
+    database-platform: org.hibernate.dialect.PostgreSQLDialect
+    hibernate:
+      ddl-auto: validate
+    properties:
+      hibernate:
+        multiTenancy: SCHEMA
+        multi_tenant_connection_provider: com.caspos.config.tenant.SchemaBasedMultiTenantConnectionProvider
+        tenant_identifier_resolver: com.caspos.config.tenant.TenantIdentifierResolver
+        format_sql: true
+        show_sql: false

src/main/resources/db/migration/master/V1__init_master_schema.sql

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+CREATE TABLE IF NOT EXISTS tenants (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    name VARCHAR(150) NOT NULL,
+    slug VARCHAR(100) UNIQUE NOT NULL,
+    db_schema VARCHAR(100) UNIQUE NOT NULL,
+    api_key VARCHAR(64) UNIQUE NOT NULL,
+    is_active BOOLEAN DEFAULT true,
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    updated_at TIMESTAMPTZ DEFAULT NOW()
+);

src/main/resources/db/migration/tenant/V1__init_tenant_schema.sql

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+-- Dining Areas
+CREATE TABLE IF NOT EXISTS dining_areas (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    name VARCHAR(100) NOT NULL,
+    is_active BOOLEAN DEFAULT true,
+    display_order INT DEFAULT 0
+);
+
+-- Restaurant Tables
+CREATE TABLE IF NOT EXISTS restaurant_tables (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    dining_area_id UUID NOT NULL REFERENCES dining_areas(id) ON DELETE CASCADE,
+    table_number VARCHAR(20) NOT NULL,
+    min_capacity INT NOT NULL DEFAULT 1,
+    max_capacity INT NOT NULL,
+    is_combinable BOOLEAN DEFAULT true,
+    pos_x DOUBLE PRECISION,
+    pos_y DOUBLE PRECISION,
+    width DOUBLE PRECISION,
+    height DOUBLE PRECISION,
+    shape VARCHAR(20) CHECK (shape IN ('RECTANGLE', 'ROUND'))
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_restaurant_tables_number_area ON restaurant_tables(table_number, dining_area_id);
+
+-- Guests
+CREATE TABLE IF NOT EXISTS guests (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    first_name VARCHAR(100),
+    last_name VARCHAR(100),
+    phone VARCHAR(50),
+    email VARCHAR(255),
+    notes TEXT,
+    no_show_count INT DEFAULT 0,
+    created_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+-- Reservations
+CREATE TABLE IF NOT EXISTS reservations (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    guest_id UUID REFERENCES guests(id),
+    start_time TIMESTAMPTZ NOT NULL,
+    end_time TIMESTAMPTZ NOT NULL,
+    guest_count INT NOT NULL,
+    status VARCHAR(30) NOT NULL CHECK (status IN ('PENDING', 'CONFIRMED', 'ARRIVED', 'FINISHED', 'NO_SHOW', 'CANCELLED')),
+    special_requests TEXT,
+    created_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_reservations_availability ON reservations(start_time, end_time, status);
+
+-- Reservation Table Assignments
+CREATE TABLE IF NOT EXISTS reservation_table_assignments (
+    reservation_id UUID NOT NULL REFERENCES reservations(id) ON DELETE CASCADE,
+    table_id UUID NOT NULL REFERENCES restaurant_tables(id) ON DELETE CASCADE,
+    PRIMARY KEY (reservation_id, table_id)
+);
+
+-- Staff Users
+CREATE TABLE IF NOT EXISTS staff_users (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    display_name VARCHAR(100) NOT NULL,
+    role VARCHAR(30) NOT NULL,
+    pin_hash VARCHAR(255) NOT NULL,
+    is_active BOOLEAN DEFAULT true
+);