v0.1.5: detect free windows in the estimate fallback + add API tests

App:
- When the single-estimate fallback sees MaxTime 0 (or an all-$0.00 ladder),
  show "Parking is currently free" instead of a bogus $0.00 purchase ladder.
  Free-detection extracted to tested client helpers (isFreeEstimate/ladderAllFree).

Client + tests (node:test, zero deps):
- src/estimates.ts: pure isFreeEstimate/ladderAllFree helpers (exported).
- test/estimates + test/http (mocked fetch): headers, query serialization,
  error->ParkSmarterApiError, rolling Auth_Token refresh, 401 clears token.
- test/integration: live checks against the Sandpoint (DSB) zones; targets the
  `test` instance by default and SKIPS when it's unreachable (non-prod is
  IP-restricted -> 403). Verified 3/3 green against prodv2 read-only.
- CI runs `npm test` as a build gate.

Note: dev/stage/test instances return 403 "Web App - Unavailable" from the
public internet (IP-restricted). API schema is otherwise unchanged vs Jul 6.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.forgejo/workflows/build-apk.yml

@@ -48,6 +48,11 @@ jobs:
       - name: Build the API client
         run: npm run build --workspace parksmarter-client
 
+      # Unit tests (mocked fetch) gate the build; integration tests skip here
+      # because the runner can't reach the IP-restricted non-prod instances.
+      - name: Run client tests
+        run: npm test --workspace parksmarter-client
+
       # RN 0.79 wants a specific NDK; install it if the image doesn't ship it (best-effort).
       - name: Ensure NDK
         run: |