Add 8 proposed changes and old trails analysis

Proposed changes (all with proposal, design, specs, tasks):
- app-navigation (9 tasks) — nav bars for both apps
- planner-landing-page (7 tasks) — standalone landing page
- planner-multiplayer-awareness (13 tasks) — participants, cursors, names
- changelog (13 tasks) — public changelog with "what's new"
- transactional-emails (15 tasks) — magic link + welcome emails
- planner-features (18 tasks) — no-go areas, notes, recovery, rate limits
- komoot-import (23 tasks) — Komoot tour import
- route-features (37 tasks) — sharing, multi-day, spatial, photos

Also adds docs/old-trails-analysis.md with feature analysis from the
older trails project.

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

openspec/changes/planner-features/specs/planner-session/spec.md

@@ -0,0 +1,8 @@
+## MODIFIED Requirements
+
+### Requirement: Planner session data model
+The Yjs document SHALL include noGoAreas and notes fields alongside waypoints and routeData.
+
+#### Scenario: Session with all fields
+- **WHEN** a Planner session is active
+- **THEN** the Yjs doc contains: waypoints (Y.Array), routeData (Y.Map), noGoAreas (Y.Array), notes (Y.Text)