[STYLE TEST] lighter colors + bold labels

Style tests for the architecture diagrams.

A. Bold / italic emphasis via Mermaid markdown-strings (the <b> workaround for strict mode):

flowchart LR
  a["`**bold** label`"] --> b["`_italic_ label`"] --> c["`normal with a **bold** word`"]

B. Lighter palette + bold service names (compare readability vs the dark boxes):

flowchart TB
  subgraph project["Docker Compose project — debiki/talkyard-*:v1.2026.003"]
    web["`**web** · OpenResty (nginx + Lua)
reverse proxy · rate + conn limits
serves /-/u/* uploads · publishes 80 + 443`"]
    app["`**app** · JVM Java 11 · Play (Scala)
talkyard-server :9000 · React SSR in-JVM
WebSocket pub-sub as in-JVM actor`"]
    cache["`**cache** · Redis 8.6.1 :6379
presence · watchbar · login secrets
link-preview cache · auto-SSL storage`"]
    rdb[("`**rdb** · PostgreSQL 18.3 :5432
all forum data`")]
    search["`**search** · Elasticsearch 9.3.1
:9200 · full-text index`"]
    rendr["`**rendr** · placeholder (sleep infinity)
no traffic today`"]
    egressp["`**egressp** · Smokescreen :4750
SSRF-filtering egress proxy`"]
    backup["`**backup** · pg_dumpall + gpg
profiles:[backup] one-shot`"]
  end
  classDef front fill:#dcfce7,stroke:#16a34a,color:#14532d
  classDef back fill:#e0e7ff,stroke:#6366f1,color:#312e81
  classDef egress fill:#fee2e2,stroke:#dc2626,color:#7f1d1d
  classDef sleepy fill:#f3f4f6,stroke:#9ca3af,color:#4b5563,stroke-dasharray:5 5
  class web,cache front
  class app,rdb,search back
  class egressp egress
  class rendr,backup sleepy

End of style test.