fix: derive PG schema from tenant ID instead of defaulting to public

Schema now defaults to tenant_${cameleer.tenant.id} (e.g. tenant_default,
tenant_acme) instead of public. Flyway create-schemas: true ensures the
schema is auto-created on first startup. CAMELEER_DB_SCHEMA env var still
available as override for feature branch isolation. Removed hardcoded
public schema from K8s base and main overlay.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/SERVER-CAPABILITIES.md

@@ -376,7 +376,7 @@ Registry: `gitea.siegeln.net/cameleer/cameleer3-server`
 | `SPRING_DATASOURCE_URL` | No | `jdbc:postgresql://localhost:5432/cameleer3` | PostgreSQL JDBC URL |
 | `SPRING_DATASOURCE_USERNAME` | No | `cameleer` | PostgreSQL user |
 | `SPRING_DATASOURCE_PASSWORD` | No | `cameleer_dev` | PostgreSQL password |
-| `CAMELEER_DB_SCHEMA` | No | `public` | PostgreSQL schema name |
+| `CAMELEER_DB_SCHEMA` | No | `tenant_{CAMELEER_TENANT_ID}` | PostgreSQL schema (override for feature branches) |
 
 ### Health Probes