Add transactional emails (SMTP) and planner features (no-go areas, notes, crash recovery)

Transactional emails:
- Add nodemailer SMTP email module with dev-mode console logging
- Magic link template and welcome template with HTML + plain text
- Wire sendMagicLink into login flow, sendWelcome into registration
- Update privacy page and deploy docs for SMTP configuration

Planner features:
- No-go areas: draw polygons on map (leaflet-geoman), synced via Yjs,
  passed to BRouter as nogos parameter, route recomputes on change
- Session notes: collaborative Y.Text textarea in sidebar tab
- Crash recovery: periodic localStorage save of Yjs state, restore on reconnect
- Rate limit session creation (10/IP/hour) in /new route

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

openspec/changes/transactional-emails/design.md

@@ -22,16 +22,15 @@ to console — users never receive it. No email infrastructure exists.
 
 ## Decisions
 
-### D1: Resend as email provider
+### D1: SMTP via nodemailer
 
-Use [Resend](https://resend.com) — simple API, generous free tier (3k
-emails/month), good developer experience. Single dependency: `resend` npm
-package.
+Use [nodemailer](https://nodemailer.com) with SMTP — standard, provider-agnostic,
+works with any SMTP server. Single dependency: `nodemailer` npm package.
+Configured via `SMTP_URL` env var (e.g., `smtp://user:pass@mail.example.com:587`).
 
-**Alternative considered**: Nodemailer + SMTP. More complex setup, requires
-SMTP server. Resend is simpler for a small project.
-
-**Alternative considered**: Postmark. Similar to Resend but less ergonomic API.
+**Alternative considered**: Resend API. Simpler initial setup but creates vendor
+dependency. SMTP is a standard protocol that works with any provider and aligns
+with the self-hostable philosophy.
 
 ### D2: Email module in apps/journal/app/lib/email.server.ts
 
@@ -50,13 +49,14 @@ text generated by stripping tags.
 
 ### D4: Sender domain: noreply@trails.cool
 
-Requires DNS verification (DKIM/SPF records) with Resend. Add TXT records via
-Terraform or manually in Hetzner DNS.
+Requires DNS records (DKIM/SPF/DMARC) for deliverability. Add TXT records
+via Terraform or manually in Hetzner DNS.
 
 ## Risks / Trade-offs
 
-- **Resend vendor lock-in** → Low risk. The `sendEmail` wrapper abstracts it.
-  Swapping to nodemailer later is a one-file change.
-- **DNS verification required** → Must add DKIM/SPF records before emails work.
-  Can use Resend's test domain initially.
-- **Free tier limits** → 3k/month is plenty for <100 users.
+- **SMTP server required** → Must provide an SMTP server. Can use any provider
+  (Mailgun, Amazon SES, Postfix, etc.) or a simple relay.
+- **DNS records required** → Must add SPF/DKIM/DMARC records for deliverability.
+- **No built-in retry** → nodemailer doesn't queue. If SMTP is down, the send
+  fails. Acceptable for current scale — welcome emails are fire-and-forget,
+  magic links can be re-requested.