Add unified search API endpoint /api/v1/search/{hash}

- Create src/api/v1/search.py with search() handler
- Add /search/{hash:str} route to v1 router
- Add tests/test_search_api.py for integration tests

Note: Tests fail until Task 3 initializes search_repository in app state.

src/api/v1/router.py

@@ -1,6 +1,6 @@
 from fastapi import APIRouter
 
-from . import blocks, fork_choice, health, index, transactions
+from . import blocks, fork_choice, health, index, search, transactions
 
 
 def create_v1_router() -> APIRouter:
@@ -14,10 +14,16 @@ def create_v1_router() -> APIRouter:
     router.add_api_route("/health/stream", health.stream, methods=["GET", "HEAD"])
     router.add_api_route("/health", health.get, methods=["GET", "HEAD"])
 
+    router.add_api_route("/search/{hash:str}", search.search, methods=["GET"])
+
     router.add_api_route("/transactions/stream", transactions.stream, methods=["GET"])
-    router.add_api_route("/transactions/list", transactions.list_transactions, methods=["GET"])
+    router.add_api_route(
+        "/transactions/list", transactions.list_transactions, methods=["GET"]
+    )
     router.add_api_route("/transactions/search", transactions.search, methods=["GET"])
-    router.add_api_route("/transactions/{transaction_hash:str}", transactions.get, methods=["GET"])
+    router.add_api_route(
+        "/transactions/{transaction_hash:str}", transactions.get, methods=["GET"]
+    )
 
     router.add_api_route("/fork-choice", fork_choice.get, methods=["GET"])
 

src/api/v1/search.py

@@ -0,0 +1,39 @@
+from http.client import BAD_REQUEST, NOT_FOUND
+from typing import TYPE_CHECKING
+
+from fastapi import Path
+from starlette.responses import JSONResponse, Response
+
+from core.api import NBERequest
+from core.types import dehexify
+
+if TYPE_CHECKING:
+    from core.app import NBE
+
+
+async def search(request: NBERequest, hash: str = Path(...)) -> Response:
+    """
+    Search for a block or transaction by hash.
+
+    Returns:
+        - 200 with {"type": "block"|"transaction", "id": int} if found
+        - 404 if not found
+        - 400 if hash is invalid
+    """
+    if not hash:
+        return Response(status_code=BAD_REQUEST)
+
+    try:
+        if hash.startswith("0x"):
+            hash = hash[2:]
+        normalized_hash = dehexify(hash)
+    except ValueError:
+        return Response(status_code=BAD_REQUEST)
+
+    result = await request.app.state.search_repository.search_by_hash(normalized_hash)
+
+    if result is None:
+        return Response(status_code=NOT_FOUND)
+
+    result_type, result_id = result
+    return JSONResponse({"type": result_type, "id": result_id})

tests/test_search_api.py

@@ -0,0 +1,28 @@
+"""Tests for Search API endpoint."""
+
+import pytest
+from fastapi.testclient import TestClient
+from src.app import create_app
+
+app = create_app("")
+client = TestClient(app)
+
+
+@pytest.mark.asyncio
+async def test_search_block_hash():
+    response = client.get("/api/v1/search/0x" + "00" * 32)
+    # Should return 404 for non-existent block
+    assert response.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_search_transaction_hash():
+    response = client.get("/api/v1/search/0x" + "11" * 32)
+    # Should return 404 for non-existent transaction
+    assert response.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_search_invalid_hash():
+    response = client.get("/api/v1/search/invalid")
+    assert response.status_code == 400