feat: add optional alias for shopping lists

[hechi]

Description

Add optional human-friendly aliases (e.g. groceries) for shopping lists, usable in place of the UUID. Aliases are unique among active lists, normalized to lowercase, and automatically cleaned up when the list expires. This prepares for a future MCP/AI
integration that will allow adding items to lists by name via voice or text.

Also switches database initialization from SchemaUtils.create() to SchemaUtils.createMissingTablesAndColumns() so the new alias column is automatically added to existing databases on deployment.

Type of Change

• New feature

What Changed

Backend (Kotlin/Ktor):

• New alias column on shopping_lists table with unique index
• GET /api/lists/by-alias/{alias} — resolve a list by its alias
• PUT /api/lists/{id}/alias — set, update, or remove a list's alias
• Full validation: lowercase alphanumeric + hyphens, 1–64 chars, rejects UUID format, 409 on conflict
• DatabaseFactory uses createMissingTablesAndColumns() for automatic schema evolution
• 11 new tests (7 route + 4 repository)

Frontend (React/TypeScript):

• Alias settings UI in the burger menu (visible when viewing a list)
• Client-side validation matching backend rules
• Save/remove with success/error feedback
• i18n keys added to both en.json and de.json

Docs:

• README: added alias to features list, API table, and security note
• CHANGELOG: entry under [Unreleased]

Testing

• Unit tests pass (npm test — 229 tests / ./gradlew test — 80 tests)
• I have added tests for new behavior (11 new backend tests)
• Manual testing performed

Backend alias endpoints tested: create, update, remove, conflict (409), not found (404), invalid format (400), UUID rejection (400). Frontend alias UI tested: set alias, edit, remove, validation feedback, conflict error display.

Checklist

• Code follows the project's style guidelines
• Documentation updated (README, CHANGELOG)
• No debug logging left in code
• No secrets or hardcoded credentials introduced
  CHANGELOG (Unreleased):

Added

• List alias — Optional human-friendly alias (e.g. groceries) for shopping lists, usable in place of the UUID; aliases are unique among active lists, normalized to lowercase, and deleted automatically when the list expires. New endpoints: GET /api/ lists/by-alias/{alias} to resolve an alias, PUT /api/lists/{id}/alias to set, update, or remove it. Small settings UI in the burger menu for managing the alias per list.

Changed

• Database schema initialization — Switched from SchemaUtils.create() to SchemaUtils.createMissingTablesAndColumns() so new columns (like alias) are automatically added to existing tables on deployment without manual migration