fix: no self-hosted ANIS model, license key is dashboard-only, remove dead ANIS_SHARE_ATTACKERS

Three corrections, driven by explicit product decisions plus code
verification:

- There is no self-hosted-ANIS deployment model going forward. ANIS_URL
  is now hardcoded to https://anis.weboria.eu in docker-compose.yml, not
  a customer-configurable env var -- removed from env.example and the
  README entirely.
- The ANIS license key is dashboard-only (Threat Intel -> ANIS
  Connection, write-only there per the earlier security fix) -- never
  set via .env. ANIS_LICENSE_KEY hardcoded to an empty string in
  docker-compose.yml (community tier by default) rather than left as a
  pass-through env var with no real path to ever being set.
- Removed ANIS_SHARE_ATTACKERS -- confirmed dead via grep, zero
  references anywhere in the Go source. This was incorrectly kept as
  "real" in the previous env.example cleanup pass; ROADMAP.md in the
  appliance repo already documented this exact variable as dead.

ANIS_ENABLED remains the one real customer-facing ANIS toggle.

docker-compose.yml

@@ -123,16 +123,19 @@ services:
       API_HOST_PORT: ${API_HOST_PORT:-9080}
       API_HOST: ${API_HOST:-}
       # ANIS community intelligence — on by default against the public
-      # Community Edition hub (empty license key = community tier, no signup
-      # required). These three only matter on first boot; manage the
-      # connection afterward from Threat Intel -> ANIS Connection in the
-      # dashboard. (No ANIS_ADMIN_KEY here: it's ANIS's own admin-dashboard
-      # credential, unrelated to the ARGUS<->ANIS protocol, which ARGUS never
-      # sends — a prior version of this file carried it by mistake.)
-      ANIS_ENABLED:          ${ANIS_ENABLED:-true}
-      ANIS_URL:              ${ANIS_URL:-https://anis.weboria.eu}
-      ANIS_LICENSE_KEY:      ${ANIS_LICENSE_KEY:-}
-      ANIS_SHARE_ATTACKERS:  ${ANIS_SHARE_ATTACKERS:-false}
+      # Community Edition hub (community tier, no signup required). There is
+      # no self-hosted-ANIS deployment model: the URL is fixed, not
+      # customer-configurable. A license key upgrades the tier, but is only
+      # ever set from Threat Intel -> ANIS Connection in the dashboard
+      # (write-only there — never round-trips back to the client), not from
+      # this file, so it's seeded empty (community tier) here.
+      # (No ANIS_ADMIN_KEY or ANIS_SHARE_ATTACKERS here: both confirmed dead
+      # via grep, zero references anywhere in internal/config.go or the ANIS
+      # client. A prior version of this file carried ANIS_ADMIN_KEY and
+      # falsely claimed ARGUS "fails closed at startup" without it.)
+      ANIS_ENABLED: ${ANIS_ENABLED:-true}
+      ANIS_URL: https://anis.weboria.eu
+      ANIS_LICENSE_KEY: ""
       DNS_SECURITY_LISTEN_ADDR: ":53"
     ports:
       - "127.0.0.1:${API_HOST_PORT:-9080}:8080"