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>

package.json

@@ -0,0 +1,27 @@
+{
+  "name": "linkder",
+  "private": true,
+  "packageManager": "pnpm@9.15.4",
+  "engines": { "node": ">=20" },
+  "scripts": {
+    "dev": "turbo run dev",
+    "build": "turbo run build",
+    "lint": "turbo run lint",
+    "typecheck": "turbo run typecheck",
+    "test": "turbo run test",
+    "test:e2e": "turbo run test:e2e",
+    "format": "prettier --write \"**/*.{ts,tsx,md,json}\"",
+    "db:generate": "pnpm --filter @linkder/db generate",
+    "db:migrate": "pnpm --filter @linkder/db migrate",
+    "db:seed": "pnpm --filter @linkder/db seed",
+    "db:studio": "pnpm --filter @linkder/db studio",
+    "services:up": "docker compose up -d postgres redis",
+    "services:down": "docker compose down"
+  },
+  "devDependencies": {
+    "@types/node": "^22.10.5",
+    "prettier": "^3.4.2",
+    "turbo": "^2.3.3",
+    "typescript": "^5.7.3"
+  }
+}