feat(message-gateway): add w_message_* models and goose migrations

internal/infra/persistence/migrator/goose/postgres/202608160003_create_message_gateway.sql

@@ -0,0 +1,40 @@
+-- +goose Up
+CREATE TABLE IF NOT EXISTS w_message_channels (
+    id BIGINT PRIMARY KEY,
+    name VARCHAR(128) NOT NULL,
+    type VARCHAR(32) NOT NULL,
+    owner_scope VARCHAR(16) NOT NULL DEFAULT 'system',
+    owner_id BIGINT NULL,
+    enabled BOOLEAN NOT NULL DEFAULT TRUE,
+    credentials TEXT NOT NULL DEFAULT '',
+    extra TEXT NOT NULL DEFAULT '',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+CREATE INDEX IF NOT EXISTS idx_w_message_channels_type ON w_message_channels (type);
+
+CREATE TABLE IF NOT EXISTS w_message_bindings (
+    id BIGINT PRIMARY KEY,
+    user_id BIGINT NOT NULL,
+    channel_id BIGINT NOT NULL,
+    platform_user_id VARCHAR(128) NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+CREATE UNIQUE INDEX IF NOT EXISTS uniq_w_message_bindings_channel_platform
+    ON w_message_bindings (channel_id, platform_user_id);
+CREATE INDEX IF NOT EXISTS idx_w_message_bindings_user ON w_message_bindings (user_id);
+
+CREATE TABLE IF NOT EXISTS w_message_pairing_codes (
+    code VARCHAR(16) PRIMARY KEY,
+    channel_id BIGINT NOT NULL,
+    platform_user_id VARCHAR(128) NOT NULL,
+    expires_at TIMESTAMPTZ NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+CREATE INDEX IF NOT EXISTS idx_w_message_pairing_lookup
+    ON w_message_pairing_codes (channel_id, platform_user_id);
+
+-- +goose Down
+DROP TABLE IF EXISTS w_message_pairing_codes;
+DROP TABLE IF EXISTS w_message_bindings;
+DROP TABLE IF EXISTS w_message_channels;