feat(mana-search): rewrite search service from NestJS to Go

Replaces the NestJS mana-search service with a Go implementation for
lower resource usage and faster startup. All 7 API endpoints are 1:1
compatible (search, extract, bulk extract, engines, health, metrics,
cache clear). Uses go-readability for content extraction and
html-to-markdown for Markdown conversion. Redis cache with graceful
degradation, Prometheus metrics, and structured JSON logging.

Binary: 22 MB vs ~200+ MB node_modules.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.macmini.yml

@@ -302,16 +302,14 @@ services:
   mana-search:
     build:
       context: .
-      dockerfile: services/mana-search/Dockerfile
+      dockerfile: services/mana-search-go/Dockerfile
     image: mana-search:local
     container_name: mana-core-search
     restart: always
     depends_on:
       searxng:
         condition: service_healthy
-      # Removed: redis - lazy connect
     environment:
-      NODE_ENV: production
       PORT: 3020
       SEARXNG_URL: http://searxng:8080
       SEARXNG_TIMEOUT: 15000
@@ -326,11 +324,11 @@ services:
     ports:
       - "3020:3020"
     healthcheck:
-      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://127.0.0.1:3020/api/v1/health"]
+      test: ["CMD", "wget", "-q", "--spider", "http://localhost:3020/health"]
       interval: 120s
       timeout: 10s
       retries: 3
-      start_period: 40s
+      start_period: 5s
 
   mana-media:
     build: