feat: add db migration for session storage

docs/DB_MIGRATION_WORKFLOW.md

@@ -26,6 +26,7 @@ Current baseline files:
 - `add_modified_on_column.sql`
 - `add_notes_column.sql`
 - `create_item_classification_table.sql`
+- `create_sessions_table.sql`
 - `multi_household_architecture.sql`
 
 ## Tracking table

packages/db/migrations/create_sessions_table.sql

@@ -0,0 +1,14 @@
+CREATE TABLE IF NOT EXISTS sessions (
+  id VARCHAR(128) PRIMARY KEY,
+  user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  expires_at TIMESTAMPTZ NOT NULL,
+  last_seen_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  user_agent TEXT
+);
+
+CREATE INDEX IF NOT EXISTS idx_sessions_user_id ON sessions(user_id);
+CREATE INDEX IF NOT EXISTS idx_sessions_expires_at ON sessions(expires_at);
+
+COMMENT ON TABLE sessions IS 'DB-backed application sessions';
+COMMENT ON COLUMN sessions.id IS 'Opaque session identifier stored in HttpOnly cookie';