feat(roadtrip): add the road trip addon with a drive-first plan view

The trip planner could show one day's route at a time and nothing across days,
so a road trip had to be pieced together in Google Maps (#1797, #435).

The addon adds a mode to the plan view rather than a tab of its own: the map
stays the workspace and gains the route over the whole trip, while the left rail
becomes one chain of stops with the driving distance and time between them and
arrival times that follow from them. A time pinned on a stop is kept and restarts
the chain, so a ferry or a museum ticket stays where the user put it.

Car bookings can finally carry the stops the schema has always allowed: the
endpoints table has held role/sequence for every transport type since #384, but
only flights and trains had an editor for them. The MCP tools already accepted
them, so this closes the gap the other way round.

Legs are fetched one at a time and spaced out — the public routing hosts answer a
whole trip's worth of requests with 429 — and the distance cap now looks at the
single leg instead of the sum, which is what dropped long drives entirely.

server/src/addons.ts

@@ -10,6 +10,7 @@ export const ADDON_IDS = {
   AIRTRAIL: 'airtrail',
   LLM_PARSING: 'llm_parsing',
   COLLECTIONS: 'collections',
+  ROADTRIP: 'roadtrip',
 } as const;
 
 export type AddonId = typeof ADDON_IDS[keyof typeof ADDON_IDS];

server/src/db/seeds.ts

@@ -120,6 +120,7 @@ function seedAddons(db: Database.Database): void {
       { id: 'mcp', name: 'MCP', description: 'Model Context Protocol for AI assistant integration', type: 'integration', icon: 'Terminal', enabled: 0, sort_order: 12 },
       { id: 'naver_list_import', name: 'Naver List Import', description: 'Import places from a shared Naver Maps list', type: 'integration', icon: 'Link2', enabled: 1, sort_order: 13 },
       { id: 'collab', name: 'Collab', description: 'Notes, polls, and live chat for trip collaboration', type: 'trip', icon: 'Users', enabled: 1, sort_order: 6 },
+      { id: 'roadtrip', name: 'Road trip', description: 'Drives with stops along the route, driving times, and arrival times that update themselves', type: 'trip', icon: 'Route', enabled: 0, sort_order: 7 },
       { id: 'journey', name: 'Journey', description: 'Trip tracking & travel journal — check-ins, photos, daily stories', type: 'global', icon: 'Compass', enabled: 0, sort_order: 35 },
       { id: 'airtrail', name: 'AirTrail', description: 'Sync flights from your AirTrail instance', type: 'integration', icon: 'Plane', enabled: 0, sort_order: 14 },
       { id: 'llm_parsing', name: 'AI Parsing', description: 'LLM fallback for booking imports kitinerary cannot read', type: 'integration', icon: 'Sparkles', enabled: 0, sort_order: 15 },