docs(examples): operator cookbook + premium-relay spec

examples/: an operator "cookbook" turning the backend's composable knobs
(registration gates, relay write policy, restore policy, feature flags) into
ready-to-run recipes per persona — personal, public-free (what the reference
instance runs), friends, paid-access, community, and paid-relay (the flagship:
free wallet + paid premium Nostr posting). Plus LEGAL_AND_OPS.md, a
not-legal-advice considerations checklist that points operators at their own
counsel and at the project's own published docs as a worked example. Recipes use
placeholders only.

docs/design/premium-relay.md: the premium-relay feature spec (reconciled to the
shipped design — dedicated premium_invoices table, transactional activate).

examples/public-free/.env.example

@@ -0,0 +1,57 @@
+# ── Recipe: public-free ──────────────────────────────────────────────────────
+# A free, open public instance — anyone can register and use the wallet; spam is
+# gated by proof-of-work, not payment. This is (minus secrets) what the reference
+# instance api.smirk.cash runs.
+#
+# Start from ../../.env.example and apply the lines below. openssl rand -hex 32
+# for each secret.
+# ─────────────────────────────────────────────────────────────────────────────
+
+SERVER_HOST=127.0.0.1
+SERVER_PORT=8081
+PUBLIC_API_URL=https://api.your-domain.example/api/v1
+ENVIRONMENT=production
+INSTANCE_ID=public-1
+
+DATABASE_URL=postgresql:///smirk_v3_db?host=/var/run/postgresql
+
+# Secrets (REQUIRED; openssl rand -hex 32 each).
+JWT_SECRET=
+SEED_FINGERPRINT_PEPPER=
+REFRESH_TOKEN_PEPPER=
+IP_SALT=
+ALTCHA_HMAC_KEY=
+ADMIN_KEY_INTEGRITY_SECRET=
+
+# Free registration, spam-gated by compute (ALTCHA proof-of-work).
+POW_REQUIRED=true
+REGISTRATION_REQUIRE_INVITE=false
+REGISTRATION_REQUIRE_PAYMENT=false
+
+# Bounded restore, PoW-priced by depth (protects your LWS/node from deep backfills;
+# a user needing more runs their own instance).
+WALLET_RESTORE_POLICY=bounded
+WALLET_MAX_RESTORE_DEPTH_DAYS=365
+WALLET_RESTORE_POW_FREE_DAYS=90
+WALLET_RESTORE_POW_DAYS_PER_BIT=30
+WALLET_RESTORE_POW_MAX_BITS=24
+
+FEATURE_PRICES=true
+FEATURE_TIPS=false
+
+# Relay off at launch. To run it, see the `friends` (locked-down) or `paid-relay`
+# (monetized) recipes.
+RELAY_ENABLED=false
+
+# Admin HTTP plane off at launch; enable + bootstrap a key when you need it.
+ADMIN_ENABLED=false
+
+# Chain endpoints — reuse your existing daemons / LWS. See ../../.env.example.
+XMR_LWS_URL=
+XMR_LWS_ADMIN_URL=
+XMR_LWS_ADMIN_KEY=
+XMR_DAEMON_URL=
+WOW_LWS_URL=
+WOW_LWS_ADMIN_URL=
+WOW_LWS_ADMIN_KEY=
+WOW_DAEMON_URL=