fix(dev): tenant-registry default port :8080 → :8090

Keycloak owns :8080 in the dev stack (docker-compose binds host:8080).
Running tenant-registry on the same port made 'make dev' refuse to
boot. Bump the default to :8090 across config, Makefile, Dockerfile,
.env.example, and README. ADDR env var still overrides if needed.

Production is unaffected — each service is in its own Orca container
with its own port-namespace.

Refs: M5.1 (unblocks portal local dev)

README.md

@@ -27,7 +27,7 @@ Multi-tenant glue: orgs, entitlements, API keys, audit. Scaffolded under milesto
 cd /path/to/platform/orca-platform && make dev-up
 
 # In another — run the service:
-make dev          # APP_ENV=dev, listens on :8080
+make dev          # APP_ENV=dev, listens on :8090 (Keycloak owns :8080 in the dev stack)
 make test         # unit tests
 make build        # compile to ./bin/tenant-registry
 ```
@@ -37,7 +37,7 @@ Env vars (override at the shell):
 | Var                | Default                                                      | Purpose                                |
 |---|---|---|
 | `APP_ENV`          | `dev`                                                        | one of `dev`, `stage`, `prod`          |
-| `ADDR`             | `:8080`                                                      | listen address                         |
+| `ADDR`             | `:8090`                                                      | listen address (avoids Keycloak's :8080) |
 | `KEYCLOAK_ISSUER`  | `http://localhost:8080/realms/breakpilot-dev`                | OIDC issuer URL                        |
 | `DATABASE_URL`     | empty (in-memory store in skeleton)                          | Postgres DSN, wired up in the M4.1 schema PR |
 
@@ -62,7 +62,7 @@ The skeleton's store is in-memory and pre-seeded with one tenant:
 }
 ```
 
-So `curl http://localhost:8080/v1/tenants/by-slug/acme` works the moment `make dev` is up.
+So `curl http://localhost:8090/v1/tenants/by-slug/acme` works the moment `make dev` is up.
 
 The full schema (tenants, tenant_products, audit_log) is committed at `migrations/0001_init.up.sql` for review, but unapplied until the M4.1 follow-up PR swaps the in-memory store for pgx-backed Postgres.
 
@@ -70,7 +70,7 @@ The full schema (tenants, tenant_products, audit_log) is committed at `migration
 
 | Env   | URL                                  | How                                  |
 |---|---|---|
-| dev   | `http://localhost:8080`          | `make dev`                           |
+| dev   | `http://localhost:8090`          | `make dev`                           |
 | stage | `https://tenant-registry.stage.breakpilot.com` | auto on merge to `main`         |
 | prod  | `https://tenant-registry.breakpilot.com`  | manual: tag `vX.Y.Z` + sign-off      |