fix: log index failures, and tidy the CSP and the API error response

Round-2 review findings.

- `_ensure_indexes` swallowed a `PyMongoError` with a bare `pass`. An index
  failure does not stop the app serving, but it means the lookup is a
  collection scan, which gets slow as the data grows — so it is now logged
  as a warning with the traceback.

- The Content-Security-Policy string is now a module-level `CSP` constant
  rather than inline in the response handler, and it gained
  `object-src 'none'` (the app uses no plugins). The test now also asserts
  that neither `unsafe-inline` nor `unsafe-eval` appears — either would
  defeat the point of the policy.

- `api_run` returned a bare dict for its 404 while the success path used
  `jsonify`. It is now `jsonify({"error": "not found"})` for consistency.

src/flask/app_factory.py

@@ -16,6 +16,26 @@ from flask_wtf import CSRFProtect
 __all__ = ["create_app"]
 
 
+#: The Content-Security-Policy the app sends with every response.
+#:
+#: The app serves only its own vendored assets — CSS, JavaScript, fonts and
+#: the logo are all in ``static/`` — so a strict ``'self'`` policy is
+#: enforceable.  There is no ``'unsafe-inline'`` anywhere, which is why the
+#: templates carry no inline scripts or style attributes.
+CSP = (
+    "default-src 'self'; "
+    "script-src 'self'; "
+    "style-src 'self'; "
+    "img-src 'self' data:; "
+    "font-src 'self'; "
+    "connect-src 'self'; "
+    "form-action 'self'; "
+    "object-src 'none'; "
+    "frame-ancestors 'none'; "
+    "base-uri 'self'"
+)
+
+
 class ImproperlyConfigured(RuntimeError):
     """Raised when the app is missing configuration it cannot safely default.
 
@@ -121,12 +141,7 @@ def create_app(config: dict | None = None) -> Flask:
         response.headers.setdefault("X-Content-Type-Options", "nosniff")
         response.headers.setdefault("X-Frame-Options", "DENY")
         response.headers.setdefault("Referrer-Policy", "same-origin")
-        response.headers.setdefault(
-            "Content-Security-Policy",
-            "default-src 'self'; script-src 'self'; style-src 'self'; "
-            "img-src 'self' data:; font-src 'self'; connect-src 'self'; "
-            "form-action 'self'; frame-ancestors 'none'; base-uri 'self'",
-        )
+        response.headers.setdefault("Content-Security-Policy", CSP)
         return response
 
     @app.errorhandler(404)

src/flask/mongo/repository.py

@@ -59,8 +59,14 @@ class BeerRepository:
                 [("beer_run_id", 1), ("date", 1)], name="run_date_1"
             )
         except PyMongoError:
-            # An index failure must not stop the app from serving.
-            pass
+            # An index failure must not stop the app from serving, but it
+            # should be visible: without the index the lookup is a collection
+            # scan, which gets slow as the data grows.
+            logger.warning(
+                "Could not create the Mongo indexes; the lookups will be "
+                "collection scans until they exist",
+                exc_info=True,
+            )
 
     # -- users -------------------------------------------------------------- #
 

src/flask/views/brews.py

@@ -196,7 +196,7 @@ def api_run(run_id: str):
     """JSON detail of a single run."""
     run = repo().run(run_id)
     if run is None:
-        return {"error": "not found"}, 404
+        return jsonify({"error": "not found"}), 404
 
     meta = repo().run_metadata(run_id)
     summary = run_summary(run, og_override=meta.get("og_points"))