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/proposal.md

@@ -0,0 +1,40 @@
+## Why
+
+The Planner's core editing works but is missing features from the architecture
+doc: no-go areas for route avoidance, session notes for collaborative planning
+communication, localStorage crash recovery for unsaved work, and rate limiting
+to protect the BRouter API from abuse on the public instance.
+
+## What Changes
+
+- **No-go areas**: Draw polygons on the map that BRouter avoids when computing
+  routes. Stored as Y.Array in the Yjs doc, synced across participants.
+- **Session notes**: Shared text area (Y.Text) for participants to leave notes,
+  discuss the route, or plan logistics. Visible in the sidebar.
+- **Crash recovery**: Periodically save Yjs state to localStorage. On
+  reconnect, merge local state with server state to recover unsaved changes.
+- **Rate limiting**: Limit session creation per IP and BRouter API calls per
+  session to prevent abuse on the public instance.
+
+## Capabilities
+
+### New Capabilities
+
+- `no-go-areas`: Draw avoidance polygons on the Planner map, passed to BRouter as routing constraints
+- `session-notes`: Shared collaborative text in Planner sessions via Yjs Y.Text
+- `crash-recovery`: localStorage backup of Yjs state for reconnection after browser crash
+- `rate-limiting`: IP-based limits on session creation and route computation
+
+### Modified Capabilities
+
+- `planner-session`: Session data model gains noGoAreas and notes fields
+- `brouter-integration`: Routing requests include no-go area polygons
+- `map-display`: Map gains polygon drawing tools for no-go areas
+
+## Impact
+
+- **Planner Yjs doc**: New fields (noGoAreas: Y.Array, notes: Y.Text)
+- **BRouter API**: No-go areas passed as `nogo` parameter
+- **Map**: Leaflet.draw or custom polygon tool for no-go areas
+- **Dependencies**: May need `leaflet-draw` for polygon editing
+- **Server**: Rate limiting middleware (in-memory store)