Initial implementation of pgvector and Oracle 26ai vector search demo

Three FastAPI backends comparing PostgreSQL/pgvector and Oracle 26ai for
semantic image search using CLIP embeddings: Python-side embedding for both
databases, plus Oracle in-database embedding via VECTOR_EMBEDDING(CLIP_TXT).

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

oravector-demo/backend/db_oracle.py

@@ -0,0 +1,19 @@
+import os
+import oracledb
+from dotenv import load_dotenv
+
+load_dotenv()
+
+def get_connection():
+    return oracledb.connect(
+        user=os.getenv("ORA_USER"),
+        password=os.getenv("ORA_PASSWORD"),
+        dsn=f"{os.getenv('ORA_HOST')}:{os.getenv('ORA_PORT')}/{os.getenv('ORA_SERVICE')}",
+    )
+
+def get_connection_indb():
+    return oracledb.connect(
+        user=os.getenv("ORA_USER_INDB"),
+        password=os.getenv("ORA_PASSWORD_INDB"),
+        dsn=f"{os.getenv('ORA_HOST')}:{os.getenv('ORA_PORT')}/{os.getenv('ORA_SERVICE')}",
+    )