feat(CF-1812): Use confluence-collab for section-based page editing

Replace inline regex section parser in voice.py with confluence_collab
library (BS4 parsing, 409 conflict retry). Bot now loads section outline
into LLM context when Confluence links are detected.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile.bot

@@ -3,4 +3,9 @@ WORKDIR /app
 RUN apt-get update && apt-get install -y --no-install-recommends ffmpeg libolm-dev && rm -rf /var/lib/apt/lists/*
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
+
+# Install confluence-collab for section-based editing (CF-1812)
+COPY confluence-collab/ /tmp/confluence-collab/
+RUN pip install --no-cache-dir /tmp/confluence-collab/ && rm -rf /tmp/confluence-collab/
+
 COPY . .