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/drizzle/meta/_journal.json

@@ -0,0 +1,13 @@
+{
+  "version": "7",
+  "dialect": "postgresql",
+  "entries": [
+    {
+      "idx": 0,
+      "version": "7",
+      "when": 1787246593084,
+      "tag": "0000_old_gorilla_man",
+      "breakpoints": true
+    }
+  ]
+}