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>

oravector-demo/sql/setup_vectors_user.sql

@@ -0,0 +1,38 @@
+-- Oracle 26ai setup for the Python-embedding backend (port 8001)
+-- Run as SYSDBA connected to FREEPDB1
+--
+-- Usage (from host):
+--   podman exec oracle.free bash -c "sqlplus -s / as sysdba @/tmp/setup_vectors_user.sql"
+--
+-- Or interactively:
+--   podman exec -it oracle.free sqlplus / as sysdba
+--   ALTER SESSION SET CONTAINER=FREEPDB1;
+--   @setup_vectors_user.sql
+
+ALTER SESSION SET CONTAINER=FREEPDB1;
+
+-- Create user
+CREATE USER vectors_user IDENTIFIED BY Vektor;
+GRANT CONNECT, RESOURCE TO vectors_user;
+GRANT UNLIMITED TABLESPACE TO vectors_user;
+
+-- Switch to vectors_user and create schema objects
+-- (run the following block connected as vectors_user)
+
+-- Table
+CREATE TABLE vectors_user.images (
+    id        NUMBER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    filename  VARCHAR2(255) NOT NULL UNIQUE,
+    filepath  VARCHAR2(1000) NOT NULL,
+    embedding VECTOR(512, FLOAT32)
+);
+
+-- HNSW vector index (requires vector_memory_size > 0 in SGA)
+CREATE VECTOR INDEX vectors_user.images_embedding_idx
+    ON vectors_user.images(embedding)
+    ORGANIZATION INMEMORY NEIGHBOR GRAPH
+    WITH DISTANCE COSINE
+    WITH TARGET ACCURACY 95
+    PARAMETERS (type HNSW, neighbors 32, efconstruction 200);
+
+EXIT;