Apply demo-activity-bot: Bruno, the synthetic public-walk generator

Adds a background demo user (`bruno`) plus two pg-boss jobs that generate
public trekking routes and activities in inner Berlin and prune them
after 14 days. Disabled by default everywhere; flip `DEMO_BOT_ENABLED`
only in prod.

- Schema: `synthetic` boolean on routes + activities
- `ensureDemoUser()` idempotent insert + badge on /users/bruno
- Generation gate: 07-21 Berlin local, p=0.12, 40-route cap in 14d
- Initial 4-walk backfill on first enable; retention via daily prune
- Prometheus gauges `demo_bot_synthetic_routes_total` / `_activities_total`
- Unit + DB-gated integration + E2E tests

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

packages/db/src/schema/journal.ts

@@ -5,6 +5,7 @@ import {
   integer,
   real,
   jsonb,
+  boolean,
   customType,
 } from "drizzle-orm/pg-core";
 
@@ -84,6 +85,12 @@ export const routes = journalSchema.table("routes", {
   tags: jsonb("tags").$type<string[]>(),
   plannerState: bytea("planner_state"),
   visibility: text("visibility").$type<Visibility>().notNull().default("private"),
+  /**
+   * Content generated by the demo-activity-bot. Set to true only on insert;
+   * never surfaced in user-facing update flows. Lets us exclude demo content
+   * from analytics and wipe all bot output with a single DELETE.
+   */
+  synthetic: boolean("synthetic").notNull().default(false),
   createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
   updatedAt: timestamp("updated_at", { withTimezone: true }).notNull().defaultNow(),
 });
@@ -118,6 +125,7 @@ export const activities = journalSchema.table("activities", {
   photos: jsonb("photos").$type<string[]>(),
   participants: jsonb("participants").$type<string[]>(),
   visibility: text("visibility").$type<Visibility>().notNull().default("private"),
+  synthetic: boolean("synthetic").notNull().default(false),
   createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
 });