feat: add site assistant component for guided tool selection

- Introduced SiteAssistant component to assist users in selecting the right tools based on their queries.
- Integrated assistant into the main App component.
- Implemented message handling and storage for user-assistant interactions.
- Added quick prompts for common user queries related to tools.
- Enhanced ToolLandingPage and DownloadButton components with SharePanel for sharing tool results.
- Updated translations for new assistant features and sharing options.
- Added API methods for chat functionality with the assistant, including streaming responses.

backend/tests/test_site_assistant_service.py

@@ -0,0 +1,105 @@
+"""Tests for site assistant persistence and fallback behavior."""
+import json
+import sqlite3
+
+from app.services.site_assistant_service import chat_with_site_assistant, stream_site_assistant_chat
+
+
+class TestSiteAssistantService:
+    def test_chat_persists_conversation_and_messages(self, app, monkeypatch):
+        with app.app_context():
+            monkeypatch.setattr(
+                'app.services.site_assistant_service._request_ai_reply',
+                lambda **kwargs: 'Use Merge PDF if you want one combined document.',
+            )
+
+            result = chat_with_site_assistant(
+                message='How can I combine PDF files?',
+                session_id='assistant-session-123',
+                fingerprint='visitor-123',
+                tool_slug='merge-pdf',
+                page_url='https://example.com/tools/merge-pdf',
+                locale='en',
+                user_id=None,
+                history=[{'role': 'user', 'content': 'Hello'}],
+            )
+
+            assert result['stored'] is True
+            assert result['session_id'] == 'assistant-session-123'
+            assert 'Merge PDF' in result['reply']
+
+            connection = sqlite3.connect(app.config['DATABASE_PATH'])
+            connection.row_factory = sqlite3.Row
+
+            conversation = connection.execute(
+                'SELECT session_id, fingerprint, tool_slug, locale FROM assistant_conversations WHERE session_id = ?',
+                ('assistant-session-123',),
+            ).fetchone()
+            messages = connection.execute(
+                'SELECT role, content FROM assistant_messages ORDER BY id ASC'
+            ).fetchall()
+
+            assert conversation['fingerprint'] == 'visitor-123'
+            assert conversation['tool_slug'] == 'merge-pdf'
+            assert conversation['locale'] == 'en'
+            assert [row['role'] for row in messages] == ['user', 'assistant']
+            assert 'How can I combine PDF files?' in messages[0]['content']
+            assert 'Merge PDF' in messages[1]['content']
+
+    def test_stream_chat_persists_streamed_reply(self, app, monkeypatch):
+        class FakeStreamResponse:
+            def raise_for_status(self):
+                return None
+
+            def iter_lines(self, decode_unicode=True):
+                yield 'data: ' + json.dumps({
+                    'choices': [{'delta': {'content': 'Use Merge '}}],
+                })
+                yield 'data: ' + json.dumps({
+                    'choices': [{'delta': {'content': 'PDF for this.'}}],
+                })
+                yield 'data: [DONE]'
+
+            def close(self):
+                return None
+
+        with app.app_context():
+            monkeypatch.setattr(
+                'app.services.site_assistant_service.check_ai_budget',
+                lambda: None,
+            )
+            monkeypatch.setattr(
+                'app.services.site_assistant_service.requests.post',
+                lambda *args, **kwargs: FakeStreamResponse(),
+            )
+            app.config.update({
+                'OPENROUTER_API_KEY': 'config-key',
+                'OPENROUTER_MODEL': 'config-model',
+            })
+
+            events = list(stream_site_assistant_chat(
+                message='How can I combine PDF files?',
+                session_id='assistant-stream-123',
+                fingerprint='visitor-123',
+                tool_slug='merge-pdf',
+                page_url='https://example.com/tools/merge-pdf',
+                locale='en',
+                user_id=None,
+                history=[{'role': 'assistant', 'content': 'Hello'}],
+            ))
+
+            assert events[0]['event'] == 'session'
+            assert events[1]['event'] == 'chunk'
+            assert events[2]['event'] == 'chunk'
+            assert events[-1]['event'] == 'done'
+            assert events[-1]['data']['reply'] == 'Use Merge PDF for this.'
+
+            connection = sqlite3.connect(app.config['DATABASE_PATH'])
+            connection.row_factory = sqlite3.Row
+            messages = connection.execute(
+                'SELECT role, content, metadata_json FROM assistant_messages ORDER BY id ASC'
+            ).fetchall()
+
+            assert [row['role'] for row in messages] == ['user', 'assistant']
+            assert messages[1]['content'] == 'Use Merge PDF for this.'
+            assert 'config-model' in messages[1]['metadata_json']