feat: add the logo, and point people at the plugin before they mint a token

Logo: the app had no icon at all — public/ held only .gitkeep and the page
emitted no <link rel="icon">, so browsers requested /favicon.ico, got a 404
and showed a blank tab. app/icon.svg is picked up automatically by the App
Router; public/logo.svg is a currentColor variant for in-app use.

The mark is three retrieval signals converging on a single memory, which is
what the search actually does (vector + full-text + tags fused by RRF) and
what the product does (many sessions, one store). Checked at 16px: the outer
strokes are held at equal opacity because asymmetry read as a rendering
artifact rather than as ranking.

Tokens page: reframed so a bearer token is the exception rather than the
default. A token is a credential to store and rotate; the plugin just signs
you in. The install hint renders only when PLUGIN_MARKETPLACE_URL is set —
a copyable command pointing nowhere is worse than no command.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -117,6 +117,8 @@ services:
       # added to .env but not listed here never reaches the container.
       OIDC_ISSUER_MCP: ${OIDC_ISSUER_MCP:-}
       OIDC_AUDIENCE_SCOPE: ${OIDC_AUDIENCE_SCOPE:-}
+      PLUGIN_MARKETPLACE_URL: ${PLUGIN_MARKETPLACE_URL:-}
+      PLUGIN_MARKETPLACE_NAME: ${PLUGIN_MARKETPLACE_NAME:-shared-memory}
 
       DATABASE_URL: postgres://${POSTGRES_USER}:${POSTGRES_PASSWORD}@db:5432/${POSTGRES_DB}