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>

apps/web/eslint.config.mjs

@@ -0,0 +1,14 @@
+import { dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { FlatCompat } from '@eslint/eslintrc';
+
+// eslint-config-next still ships a legacy config, so it needs the compat shim
+// to run under ESLint 9 flat config.
+const compat = new FlatCompat({ baseDirectory: dirname(fileURLToPath(import.meta.url)) });
+
+const config = [
+  { ignores: ['.next/**', 'node_modules/**', 'next-env.d.ts'] },
+  ...compat.extends('next/core-web-vitals', 'next/typescript'),
+];
+
+export default config;