Merge the monetization feature branch.

Add RYS Premium subscription system

Introduce optional paid tier with sign-in, Stripe billing, and premium
feature gating. Core features remain free. Includes Node.js server for
auth, payments, and license management.

Extension changes:
- Sign-in flow with magic link email
- Premium/upgrade/account modals with branded UI
- Premium feature gating (60+ advanced settings)
- Password lock and scheduling (premium)
- Fix "hide all but first row" for YouTube's new flat homepage DOM
- Hide sidebar ad panels by default
- Enable "Hide all Shorts" by default

Server:
- Magic link auth with rate limiting
- Stripe checkout, webhooks, and billing portal
- JWT-based license tokens
- AWS SES transactional emails (welcome, sign-in, cancellation)
- Grandfathered donor support

Also adds CI workflow, server test suite, and extension unit tests.

server/README.md

@@ -0,0 +1,72 @@
+# RYS Premium Server
+
+Backend server for the premium subscription system.
+
+## Quick Start
+
+```bash
+# Install dependencies
+npm install
+
+# Copy env and fill in values
+cp .env.example .env
+
+# Run tests
+npm test
+
+# Start development server
+npm run dev
+
+# Start production server
+npm start
+```
+
+## API Endpoints
+
+| Endpoint | Method | Auth | Description |
+|----------|--------|------|-------------|
+| `/health` | GET | No | Health check |
+| `/auth/send-magic-link` | POST | No | Send magic link email |
+| `/auth/verify` | GET | No | Magic link target (HTML) |
+| `/auth/poll` | GET | No | Poll for verification status |
+| `/license/check` | GET | Yes | Check premium status |
+| `/checkout/create` | POST | Yes | Create Stripe checkout session |
+| `/checkout/success` | GET | No | Success page (HTML) |
+| `/checkout/cancel` | GET | No | Cancel page (HTML) |
+| `/billing/portal` | POST | Yes | Create billing portal session |
+| `/billing/return` | GET | No | Return page (HTML) |
+| `/webhook/stripe` | POST | No* | Stripe webhook |
+
+*Authenticated via Stripe signature
+
+## File Structure
+
+```
+server/
+├── src/
+│   ├── index.js        # Entry point
+│   ├── config.js       # Configuration
+│   ├── routes/         # Express routes
+│   ├── services/       # Stripe, JWT, email
+│   └── storage/        # File-based storage
+├── data/
+│   ├── grandfathered.json   # Donor emails (gitignored)
+│   ├── auth-requests/       # Pending auth (auto-created)
+│   └── rate-limits/         # Rate limit counters (auto-created)
+├── tests/
+└── package.json
+```
+
+## Grandfathered Users
+
+Past donors get lifetime premium. Store emails in `data/grandfathered.json`:
+
+```json
+["donor1@example.com", "donor2@example.com"]
+```
+
+This file is gitignored. See `data.example/` for format.
+
+## Full Documentation
+
+See [DEPLOYMENT.md](../DEPLOYMENT.md) for complete setup, deployment, and testing instructions.