Add Basic Auth and optimize Docker build

Dockerfile

@@ -1,8 +1,17 @@
 FROM python:3.11-slim
 WORKDIR /app
-COPY . .
+
+# 1. Install System Deps (ffmpeg) FIRST
+# These rarely change, so Docker will cache this layer forever.
 RUN apt-get update && apt-get install -y ffmpeg && rm -rf /var/lib/apt/lists/*
-RUN pip install --no-cache-dir requests flask
-RUN mkdir -p /app/data
-EXPOSE 5000
-CMD ["python", "ta_symlink.py"]
+
+# 2. Install Python Deps SECOND
+# Only re-runs if requirements.txt changes
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+# 3. Copy Code LAST
+# Now, if you change code, only this fast step re-runs.
+COPY . .
+
+CMD ["python", "ta_symlink.py"]