feat: RBAC, atomic deployments, fleet backups, and licensing (Pro) (#185)

* feat: add RBAC viewer accounts, atomic deployments, and fleet-wide backups (Pro)

Introduces three Pro-tier features:

- RBAC: Multi-user system with admin/viewer roles, user management UI,
  automatic migration from single-admin credentials, viewer restrictions
  across the entire UI (read-only editor, hidden action buttons)

- Atomic Deployments: Pre-deploy file backup to .sencho-backup/, automatic
  rollback on health probe failure, manual rollback button, health probes
  added to stack updates, webhook-triggered deploys use atomic rollback

- Fleet-Wide Backups: Point-in-time snapshots of compose files across all
  nodes (local + remote), stored centrally in SQLite, per-stack restore
  with optional redeploy, graceful handling of offline nodes

* fix(settings): use correct ProGate prop name in UsersSection

* fix(settings): remove unused isPro prop from UsersSection

* fix(auth): fetch user info after login and setup so isAdmin is set correctly

* feat(pricing): revise pricing strategy and enforce variant-based seat limits

Raise Personal Pro from $49/yr to $69/yr with 3 viewer seats (up from 1).
Add $15/mo billing option for Team Pro. Mark lifetime pricing as a
90-day early-adopter offer. Store Lemon Squeezy variant_name on
activation/validation and enforce seat limits server-side per variant.

* feat(licensing): add Lemon Squeezy checkout, webhook, and billing portal integration

Server-side checkout URL generation (POST /api/checkout) with admin email
pre-fill and instance_id custom data. HMAC-SHA256 verified webhook endpoint
(POST /api/webhooks/lemonsqueezy) handling order, subscription, and payment
lifecycle events for automatic license activation. Customer billing portal
link stored from webhook events and exposed via GET /api/billing/portal.
In-app checkout buttons in Settings with manual license key fallback.

* fix(licensing): exempt Lemon Squeezy webhook from auth middleware

The catch-all auth middleware on /api/* was blocking the public webhook
endpoint. Added /webhooks/lemonsqueezy to the exemption list alongside
/auth/* and /webhooks/:id/trigger.

* feat(pricing): update pricing to final live rates

Personal Pro: $7.99/month, $69.99/year, $249 lifetime.
Team Pro: $49.99/month, $499.99/year, $1,499 lifetime.
Added personal_monthly checkout variant across backend, frontend, and website.

* refactor(licensing): remove server-side checkout/webhook for self-hosted model

Sencho is self-hosted — each user runs their own instance, so there is
no central server to receive webhooks or hold the store API key. Replaced
in-app checkout buttons with a "View Pricing" redirect to sencho.io and
kept manual license key activation as the primary flow.

- Delete LemonSqueezyService (checkout, webhook, HMAC verification)
- Remove POST /api/checkout, GET /api/billing/portal, POST /api/webhooks/lemonsqueezy
- Remove raw body parser and auth exemption for webhook route
- Remove all LEMONSQUEEZY_* env vars from .env.example
- Replace checkout buttons in SettingsModal with single "View Pricing" button
- Simplify LicenseContext checkout to open sencho.io pricing page
- Update licensing docs to reflect website-based purchase flow

* chore: normalize em-dashes to hyphens across codebase (linter)

* chore: remove accidentally tracked directories from index

docs/operations/backup.mdx

@@ -14,13 +14,13 @@ Sencho stores all its state in two places: the **data directory** (SQLite databa
 Default path: `/app/data` inside the container, mapped to wherever you mounted it on the host (e.g. `./sencho-data`).
 
 Contains:
-- `sencho.db` — SQLite database with all settings, nodes, alerts, metrics history, and notification history
+- `sencho.db` - SQLite database with all settings, nodes, alerts, metrics history, and notification history
 
 This single file is everything Sencho knows about itself. Back it up and you can fully restore any Sencho installation.
 
 ### 2. Compose directory (`COMPOSE_DIR`)
 
-The directory containing your stack subdirectories — your `compose.yaml` files, `.env` files, and any bind-mounted config files stored there.
+The directory containing your stack subdirectories - your `compose.yaml` files, `.env` files, and any bind-mounted config files stored there.
 
 This is your actual application data. It lives entirely outside Sencho and you almost certainly already have it on a schedule, but include it in any Sencho backup plan.
 
@@ -131,7 +131,7 @@ If other Sencho instances were pointing to your old host as a remote node, updat
 | Item | Location | Notes |
 |------|----------|-------|
 | Container data volumes | Wherever each stack's volumes are mounted on the host | Back these up separately per-application |
-| Actual container images | Docker image cache | These are re-pulled on next deploy — no backup needed |
+| Actual container images | Docker image cache | These are re-pulled on next deploy - no backup needed |
 | Sencho logs (docker logs) | Container stdout | Not persisted beyond container lifetime |
 
 <Note>