fix(subscription): add weekly digest subscribe feedback and fix base URL

[NayansiDupare]

Summary

Resolves the lack of visual feedback when subscribing to the Weekly Digest in the footer and fixes the Mixed Content / incorrect API base URL routing on the live site. Also addresses a lifespan console startup crash on Windows.

Related Issue

Closes #1058

Changes

• Frontend:
  • Updated getApiBase() in frontend/index.html to resolve to window.location.origin when running on a web server instead of hardcoding localhost:8000.
  • Added an inline digestFeedback container in the footer with success/error/loading visual cues (custom SVG icons, text colors matching design tokens) and toasts.
  • Added an input listener to dynamically clear feedback once the user edits the email field.
• Backend:
  • Replaced emojis and horizontal ellipsis … in backend/app/main.py lifespan print/logging statements to prevent UnicodeEncodeError crashes on Windows CP1252 consoles.
  • Automatically call Base.metadata.create_all(bind=engine) at startup lifespan to build SQLAlchemy ORM tables (like digest_subscriptions) for clean setups.
• Testing:
  • Converted frontend/tests/helpers.js and frontend/tests/e2e/analyze.spec.js to ES module syntax to match the tests/package.json configuration.
  • Added an E2E Playwright test case checking that subscribing to the digest correctly triggers the backend API and renders success feedback.

How to Test

1. Start the backend: uvicorn app.main:app --reload
2. Open the app (http://localhost:8000/app/)
3. Scroll to the footer, type a valid email in the "Weekly Digest" input, and click Subscribe.
4. Verify visual success feedback is rendered and input is cleared.
5. Re-type the same email and click Subscribe to verify error feedback is displayed ("already subscribed").

[imDarshanGK]

Please add a short video demo showing the weekly digest subscribe flow with success/error feedback and base URL fix.