feat: modernize app for current TF, fix broken UI, add tests + hygiene

App:
- Replace removed predict_classes() with model.predict() + 0.5 threshold
- Return JSON {label, pneumonia, confidence} instead of a bare string
- Create uploads dir on demand; delete uploaded X-rays after inference
- Lazy model loading with a clear error when cnn_model.h5 is absent
- Add /health probe, file-type + size validation, real error handling
- Drop obsolete TF1 graph/gevent cruft

Frontend:
- Fix example images (were D:\ Windows paths) to static/images via url_for
- Remove stray 'ships sunk by icebergs' redirect
- Swap defunct cdn.bootcss.com for jsDelivr; fix malformed form action
- Render label + confidence and surface API errors in the UI

Project hygiene:
- Add requirements.txt, MIT LICENSE, DISCLAIMER.md (medical)
- Add pytest smoke tests that mock TensorFlow (no 1GB wheel in CI)
- Add GitHub Actions CI (byte-compile + tests)
- Rewrite README (accurate run steps, API, Limitations)
- Parametrize notebook dataset path via DATA_DIR; fix fit_generator/predict_classes

Author: Sanjays2402

.github/workflows/ci.yml

@@ -0,0 +1,29 @@
+name: CI
+
+on:
+  push:
+    branches: [main, "feat/**", "fix/**"]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install lightweight deps (no TensorFlow in CI)
+        run: |
+          python -m pip install --upgrade pip
+          pip install flask numpy Pillow pytest
+
+      - name: Byte-compile sources
+        run: python -m compileall app.py
+
+      - name: Run smoke tests (TensorFlow mocked)
+        run: pytest -q