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>

turbo.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://turbo.build/schema.json",
+  "globalDependencies": [".env"],
+  "globalEnv": [
+    "NODE_ENV",
+    "DATABASE_URL",
+    "REDIS_URL",
+    "AUTH_SECRET",
+    "AUTH_URL",
+    "NEXT_PUBLIC_APP_URL"
+  ],
+  "tasks": {
+    "build": { "dependsOn": ["^build"], "outputs": [".next/**", "!.next/cache/**", "dist/**"] },
+    "dev": { "cache": false, "persistent": true },
+    "lint": { "dependsOn": ["^build"] },
+    "typecheck": { "dependsOn": ["^build"] },
+    "test": { "dependsOn": ["^build"], "outputs": ["coverage/**"] },
+    "test:e2e": { "dependsOn": ["^build"], "cache": false }
+  }
+}