fix(passport-photo): require the face-detection bundle, not just background-removal (#329)

* fix(passport-photo): require the face-detection bundle, not just background-removal

Passport Photo runs face-landmark detection (face_landmarks.py, gated to the
face-detection bundle) before background removal (background-removal bundle),
but it was only declared under and guarded against background-removal. A user
who installed only Background Removal passed every JS-side check, then hit a
late "feature_not_installed" from the Python dispatcher gate when the analyze
step ran face landmarks, and the UI never told them Face Detection was needed.

- shared: add TOOL_EXTRA_BUNDLES + getRequiredBundlesForTool so a tool can
  declare more than one required bundle (passport-photo needs background-removal
  and face-detection). enablesTools is untouched, so the one-tool-per-bundle
  invariant still holds.
- api: isToolInstalled() now checks every required bundle; add
  getFirstMissingBundleForTool() so the analyze and base routes, pipeline (both
  guards) and batch report the bundle the user actually still needs.
- web: the proactive install prompt (tool-page) and features-store treat a tool
  as installed only when all required bundles are present, and point the prompt
  at the first missing one (sequential install, no new UI).

Refs #327

* test(passport-photo): deterministic integration coverage for the two-bundle guard

Boots the real API with an isolated DATA_DIR and controls installed.json to
prove the HTTP route behavior end-to-end:
- nothing installed -> 501 naming background-removal
- only background-removal installed -> 501 naming face-detection (issue #327)
- both installed -> guard passes (not 501)
- base route reports face-detection too

Refs #327

tests/unit/web/features-store.test.ts

@@ -197,6 +197,29 @@ describe("useFeaturesStore", () => {
 
       expect(useFeaturesStore.getState().isToolInstalled("remove-background")).toBe(false);
     });
+
+    // passport-photo needs background-removal AND face-detection (issue #327).
+    it("returns false for passport-photo when only background-removal is installed", () => {
+      useFeaturesStore.setState({
+        bundles: [
+          makeBundleState({ id: "background-removal", status: "installed" }),
+          makeBundleState({ id: "face-detection", status: "not_installed" }),
+        ],
+      });
+
+      expect(useFeaturesStore.getState().isToolInstalled("passport-photo")).toBe(false);
+    });
+
+    it("returns true for passport-photo only when both required bundles are installed", () => {
+      useFeaturesStore.setState({
+        bundles: [
+          makeBundleState({ id: "background-removal", status: "installed" }),
+          makeBundleState({ id: "face-detection", status: "installed" }),
+        ],
+      });
+
+      expect(useFeaturesStore.getState().isToolInstalled("passport-photo")).toBe(true);
+    });
   });
 
   describe("getBundleForTool()", () => {
@@ -221,6 +244,16 @@ describe("useFeaturesStore", () => {
       const result = useFeaturesStore.getState().getBundleForTool("remove-background");
       expect(result).toBeNull();
     });
+
+    it("points at the first missing required bundle for a multi-bundle tool", () => {
+      const bg = makeBundleState({ id: "background-removal", status: "installed" });
+      const face = makeBundleState({ id: "face-detection", status: "not_installed" });
+      useFeaturesStore.setState({ bundles: [bg, face] });
+
+      // passport-photo needs both; background-removal is installed, so the
+      // prompt should ask for face-detection.
+      expect(useFeaturesStore.getState().getBundleForTool("passport-photo")).toEqual(face);
+    });
   });
 
   describe("clearError()", () => {