Remove LinkedIn Profile URL and Phone number fields from demo form

Summary

This PR removes the LinkedIn Profile URL and Phone number fields from the reflex-ui demo form to streamline the user experience. The changes include:

• Removed fields: linkedin_url and phone_number from the DemoEvent dataclass
• Updated form UI: Removed the LinkedIn Profile URL and Phone number input fields from the form component
• External service updates: Removed linkedinUrl and phoneNumber from Slack webhook payload
• Notes content: Removed LinkedIn URL reference from enterprise follow-up notes
• Cal.com URL update: Changed small company URL from "reflex-intro" to "reflex-intro-call" per user request
• Testing addition: Added /demo-form route to demo app for easier testing

Review & Testing Checklist for Human

• End-to-end form submission test: Submit the demo form with valid data and verify it processes successfully without errors (I couldn't complete this due to CSS styling issues making form fields non-interactable)
• External service integration verification: Check that Slack webhook, PostHog, and CommonRoom integrations still work correctly without the removed fields
• Cal.com URL validation: Test both small company (<10 employees) and large company routing to ensure the new "reflex-intro-call" URL works correctly
• Visual form layout check: Verify the form looks good and has proper spacing/alignment without the removed fields
• Runtime error check: Monitor browser console and server logs during form submission for any errors related to missing field references

Recommended test plan:

1. Navigate to /demo-form route in the demo app
2. Fill out the form with valid company email and required fields
3. Test both small company (1-10 employees) and large company (11+ employees) scenarios
4. Verify successful redirects to appropriate Cal.com URLs
5. Check that external services receive expected data without the removed fields

Diagram

%%{ init : { "theme" : "default" }}%%
graph TB
    DemoForm["reflex_ui/blocks/<br/>demo_form.py"]:::major-edit
    DemoApp["demo/demo/<br/>demo.py"]:::minor-edit
    DemoEvent["DemoEvent<br/>dataclass"]:::major-edit
    FormUI["Form UI<br/>get_component()"]:::major-edit
    
    Slack["Slack<br/>Webhook"]:::context
    PostHog["PostHog<br/>Analytics"]:::context  
    CommonRoom["CommonRoom<br/>CRM"]:::context
    CalCom["Cal.com<br/>Booking"]:::context
    
    DemoForm --> DemoEvent
    DemoForm --> FormUI
    DemoApp --> DemoForm
    
    DemoEvent --> Slack
    DemoEvent --> PostHog
    DemoEvent --> CommonRoom
    DemoForm --> CalCom
    
    subgraph Legend
        L1[Major Edit]:::major-edit
        L2[Minor Edit]:::minor-edit  
        L3[Context/No Edit]:::context
    end

    classDef major-edit fill:#90EE90
    classDef minor-edit fill:#ADD8E6
    classDef context fill:#FFFFFF

Notes

• The form previously collected LinkedIn Profile URL and Phone number as optional fields, but these have been completely removed to simplify the user experience
• All external service integrations (Slack, PostHog, CommonRoom) have been updated to not send these fields
• The Cal.com URL change affects the routing logic for companies with fewer than 10 employees
• Added a test route at /demo-form to make it easier to test the form functionality

Session Info: Requested by Alek (@Alek99)
Link to Devin run: https://app.devin.ai/sessions/5a8a56e988b04971977b7e0beb043a60