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/route-features/specs/spatial-search/spec.md

@@ -0,0 +1,12 @@
+## ADDED Requirements
+
+### Requirement: Map-based route discovery
+Users SHALL be able to discover public routes by browsing a map.
+
+#### Scenario: Browse routes on map
+- **WHEN** a user visits the route explore page and pans/zooms the map
+- **THEN** public routes within the visible area are shown as polylines on the map
+
+#### Scenario: Route preview
+- **WHEN** a user clicks a route on the explore map
+- **THEN** a popup or sidebar shows the route name, distance, elevation, and a link to the detail page