Add project scope documentation for AI playgroup registration system

Define complete non-technical scope for replacing Google Forms registration
with an AI-powered conversational agent. Includes:

- Registration data requirements (13 fields with validation rules)
- Knowledge base content (fees, regulations, schedule, FAQ from official PDFs)
- Conversation flow design with bilingual support (German/English)
- Agent personality guidelines (warm & friendly tone)
- Admin notification routing by playgroup type
- Email reminder system for incomplete registrations
- Data export formats (CSV/JSON)
- Channel configuration (email + chat)
- Release priorities (MVP scope defined)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

openspec/changes/define-project-scope/specs/chat-interface/spec.md

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+## ADDED Requirements
+
+### Requirement: Web-based chat interface
+The system SHALL provide a web-based chat interface where parents can interact with the AI agent in real-time.
+
+#### Scenario: Parent accesses chat
+- **WHEN** a parent navigates to the chat interface URL
+- **THEN** they SHALL see a chat window ready for conversation
+
+#### Scenario: Real-time messaging
+- **WHEN** a parent sends a message in the chat
+- **THEN** the agent's response SHALL appear without requiring a page refresh
+
+### Requirement: Chat interface is mobile-responsive
+The system SHALL provide a chat interface that works well on mobile devices and desktop browsers.
+
+#### Scenario: Mobile device access
+- **WHEN** a parent accesses the chat on a mobile device
+- **THEN** the interface SHALL be usable without horizontal scrolling or zooming
+
+#### Scenario: Desktop access
+- **WHEN** a parent accesses the chat on a desktop browser
+- **THEN** the interface SHALL utilize the available screen space appropriately
+
+### Requirement: Chat displays conversation history
+The system SHALL display the conversation history within the current session.
+
+#### Scenario: Message history visible
+- **WHEN** a parent is in an active chat session
+- **THEN** they SHALL see all previous messages in the current conversation
+
+#### Scenario: Clear message attribution
+- **WHEN** viewing the chat history
+- **THEN** parent messages and agent messages SHALL be visually distinguishable
+
+### Requirement: Chat session management
+The system SHALL manage chat sessions to maintain conversation context.
+
+#### Scenario: Session persistence
+- **WHEN** a parent refreshes the page during a chat session
+- **THEN** the conversation history and state SHALL be preserved
+
+#### Scenario: Session timeout notification
+- **WHEN** a chat session has been inactive for an extended period
+- **THEN** the system SHALL notify the parent before ending the session
+
+### Requirement: Chat interface provides typing indicators
+The system SHALL indicate when the agent is processing a response.
+
+#### Scenario: Agent processing
+- **WHEN** the agent is generating a response
+- **THEN** the chat interface SHALL display a typing or processing indicator