Add SQL setup scripts for all three backends

- pgvector-demo/sql/setup.sql: enable pgvector extension, create images table and HNSW index
- oravector-demo/sql/setup_vectors_user.sql: create vectors_user, images table and HNSW vector index
- oravector-demo/sql/setup_vector_schema.sql: create VECTOR user, load CLIP ONNX models, create FOTO_VEKTOR table

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pgvector-demo/sql/setup.sql

@@ -0,0 +1,17 @@
+-- PostgreSQL setup for pgvector demo
+-- Run as superuser (dl) against the vectors_demo database
+--
+-- Usage:
+--   docker exec -i postgresql-database-1 psql -U dl -d vectors_demo -f - < pgvector-demo/sql/setup.sql
+
+CREATE EXTENSION IF NOT EXISTS vector;
+
+CREATE TABLE IF NOT EXISTS images (
+    id        SERIAL PRIMARY KEY,
+    filename  TEXT NOT NULL UNIQUE,
+    filepath  TEXT NOT NULL,
+    embedding vector(512)
+);
+
+CREATE INDEX IF NOT EXISTS images_embedding_idx
+    ON images USING hnsw (embedding vector_cosine_ops);