docs(dev): Running locally + tests README; add Meilisearch to compose; env defaults

Single docker compose (Postgres + Meilisearch) for dev and tests. .env.example
now works out-of-the-box (SESSION_COOKIE_SECURE=false for http://localhost login;
MEILI_* matching compose).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -9,6 +9,24 @@ services:
       - "5432:5432"
     volumes:
       - pgdata:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+
+  meilisearch:
+    image: getmeili/meilisearch:v1.12
+    environment:
+      # Development mode relaxes the production master-key length requirement and
+      # enables the search-preview UI. The key below is for local use only.
+      MEILI_ENV: development
+      MEILI_MASTER_KEY: masterKey
+    ports:
+      - "7700:7700"
+    volumes:
+      - meilidata:/meili_data
 
 volumes:
   pgdata:
+  meilidata: