feat: upgrade Docker image to python:3.14-slim-bookworm

Bump base image from 3.10 to 3.14 to match host Python version.
Add pip cache purge after install to reduce image size.

Note: spaCy remains commented out (no 3.14 wheel yet).
All other dependencies verified working on Python 3.14.4.

Co-Authored-By: RuFlo <ruv@ruv.net>

CLAUDE.md

@@ -5,7 +5,7 @@
 **VideoMakerBot** — Automated short-form video creator from social media content.
 
 **Status:** Production-ready, actively maintained (v3.4.0)
-**Language:** Python 3.14+ (host); Docker image uses python:3.10-slim-bookworm for stability
+**Language:** Python 3.14+ (host + Docker image)
 **Runtime:** **Docker only** — all CLI, GUI, and test invocations go through `docker compose`. Do not invoke `python` on the host.
 **Platforms:** Reddit (PRAW API), Threads (Graph API + Web Scraping)
 
@@ -320,7 +320,7 @@ Last 1-4: engagement metrics (likes, replies, reposts, quotes)
 | `utils/background_audios.json` | Background audio manifest |
 | `utils/gui_utils.py` | `add_background`, `delete_background`, `modify_settings`, `get_checks` (no eval) |
 | `GUI.py` | Flask app: `/`, `/video/<id>`, `/backgrounds`, `/settings`, `/create`; CSRF + security headers |
-| `Dockerfile` | python:3.10-slim-bookworm + ffmpeg + Playwright Chromium + pytest; runs as `appuser` |
+| `Dockerfile` | python:3.14-slim-bookworm + ffmpeg + Playwright Chromium + pytest; runs as `appuser` |
 | `docker-compose.yml` | Three services: `gui` (port 4000), `cli`, `test` |
 | `tests/test_gui_utils.py` | Pytest regression for Background Manager round-trip |
 

Dockerfile

@@ -1,5 +1,4 @@
-# For production, pin to a digest: FROM python:3.10-slim-bookworm@sha256:...
-FROM python:3.10-slim-bookworm
+FROM python:3.14-slim-bookworm
 
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1 \
@@ -15,10 +14,11 @@ RUN apt-get update \
     && rm -rf /var/lib/apt/lists/*
 
 COPY requirements.txt ./
-# Pin pip for reproducible builds: --upgrade pip==24.0
+# Pin pip for reproducible builds: --upgrade pip==25.x
 RUN pip install --upgrade pip \
     && pip install -r requirements.txt \
-    && pip install pytest
+    && pip install pytest \
+    && pip cache purge
 
 RUN python -m playwright install --with-deps chromium