fix(journal): architectural audit omnibus

Addresses 8 issues from the Journal architecture audit:

1. DB indexes on routes.ownerId + activities.ownerId. Listing queries on
   these tables were full table scans; adds composite indexes matching
   the order-by columns (updatedAt/startedAt/createdAt).
2. Zod validation on /api/auth/register body. Previously the action
   destructured request.json() with zero schema validation.
3. N+1 GeoJSON batch fetch collapsed to a single ANY($1::text[]) query
   in both routes.server and activities.server.
4. Webhook envelope validation in /api/sync/webhook/:provider.
5. AbortSignal.timeout(30s) on all external fetches (Komoot, Wahoo) via
   a new fetchWithTimeout helper in lib/http.server.ts.
6. .limit(100) on listPublicRoutesForOwner / listPublicActivitiesForOwner.
9. Welcome email moved off fire-and-forget onto a pg-boss job with
   retryLimit: 3 (send-welcome-email).
10. process.env.ORIGIN ?? "http://localhost:3000" centralized into
    lib/config.server.ts::getOrigin() across 14 call sites.

Issues 7 (centralized apiError/auth guards across 60+ route files) and
8 (split .server.ts boundaries across 20+ route files) intentionally
deferred — both are pure refactors that would balloon this PR past
reviewability and warrant their own focused PRs.

Tests added:
- lib/config.server.test.ts (2 cases)
- lib/http.server.test.ts (3 cases — timeout abort, success passthrough,
  caller-signal composition)
- routes/api.sync.webhook.$provider.test.ts (6 cases)
- routes/api.auth.register.test.ts (7 cases — schema rejection paths +
  the new welcome-email enqueue assertion)

Full repo: pnpm typecheck, pnpm lint, pnpm test all green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/db/src/schema/journal.ts

@@ -107,7 +107,9 @@ export const routes = journalSchema.table("routes", {
   synthetic: boolean("synthetic").notNull().default(false),
   createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
   updatedAt: timestamp("updated_at", { withTimezone: true }).notNull().defaultNow(),
-});
+}, (t) => ({
+  ownerUpdatedIdx: index("routes_owner_updated_idx").on(t.ownerId, t.updatedAt.desc()),
+}));
 
 export const routeVersions = journalSchema.table("route_versions", {
   id: text("id").primaryKey(),
@@ -141,7 +143,11 @@ export const activities = journalSchema.table("activities", {
   visibility: text("visibility").$type<Visibility>().notNull().default("private"),
   synthetic: boolean("synthetic").notNull().default(false),
   createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
-});
+}, (t) => ({
+  // Hot paths: listActivities (sort by started_at) and listPublicActivitiesForOwner.
+  ownerStartedIdx: index("activities_owner_started_idx").on(t.ownerId, t.startedAt.desc()),
+  ownerCreatedIdx: index("activities_owner_created_idx").on(t.ownerId, t.createdAt.desc()),
+}));
 
 // --- OAuth2 PKCE (mobile app auth) ---