M0: foundation — monorepo, PostGIS schema, deck query, app shell

Greenfield scaffold for Linkder, a swipe-to-hire marketplace for local
professional services.

- pnpm/turbo monorepo: apps/web, packages/{shared,db}
- Postgres 16 + PostGIS via docker compose (ports 5442/6389 to avoid
  clashing with other local stacks)
- Drizzle schema, 23 tables, geography(Point,4326) with GiST indexes
- Domain core in packages/shared: integer-cent money, status transition
  graphs, deck ranking weights, cancellation policy — 46 unit tests
- Deck query: filtering in Postgres on the GiST index, ranking in JS so
  the weights stay tunable — 18 integration tests against a seeded DB
- Deterministic seed placing pros at known distances, including three
  that must NOT appear on a deck (out of radius, unverified, away)
- Next.js 15 app shell with a working swipe deck
- CI: typecheck, lint, test, build against live postgres+redis

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

packages/db/vitest.config.ts

@@ -0,0 +1,14 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    environment: 'node',
+    include: ['test/**/*.test.ts'],
+    // Integration tests share one seeded database — running them in parallel
+    // would have them deleting each other's swipes.
+    fileParallelism: false,
+    sequence: { concurrent: false },
+    testTimeout: 20_000,
+    hookTimeout: 20_000,
+  },
+});