Add reMarkable backup system with web UI

- Docker container with rmapi cloud backup, PDF conversion pipeline
- Web UI: file browser, multi-select, delete/move, thumbnail preview
- Sync: backup from reMarkable cloud, rmdoc→PDF conversion via rmc+Inkscape
- Excluded-files mechanism to prevent deleted items from returning after sync

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

remarkable/Dockerfile

@@ -0,0 +1,51 @@
+FROM ubuntu:24.04
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && apt-get install -y \
+    rsync curl unzip python3 python3-pip \
+    inkscape poppler-utils cron \
+    php-cli \
+    && rm -rf /var/lib/apt/lists/*
+
+# rmc + Farb-Patch
+RUN pip3 install "rmc==0.3.0" "rmscene>=0.7.0" "pypdf" "rmrl" --break-system-packages --ignore-installed packaging \
+    && python3 - <<'EOF'
+import pathlib
+import rmc.exporters.writing_tools as m
+f = pathlib.Path(m.__file__)
+src = f.read_text()
+src = src.replace(
+    "self.base_color = RM_PALETTE[base_color_id]",
+    "self.base_color = RM_PALETTE.get(base_color_id, (255, 235, 0) if base_color_id == 9 else (128, 128, 128))"
+)
+old = '        segment_color = [min(int(abs(intensity - 1) * 255), 60)] * 3\n        return "rgb" + str(tuple(segment_color))'
+new = '        r = min(int(self.base_color[0] * intensity), 255)\n        g = min(int(self.base_color[1] * intensity), 255)\n        b = min(int(self.base_color[2] * intensity), 255)\n        return "rgb" + str((r, g, b))'
+src = src.replace(old, new)
+old_b = '        segment_color = [int(rev_intensity * (255 - self.base_color[0])),\n                         int(rev_intensity * (255 - self.base_color[1])),\n                         int(rev_intensity * (255 - self.base_color[2]))]\n        return "rgb" + str(tuple(segment_color))'
+new_b = '        segment_color = [int(255 - intensity * (255 - c)) for c in self.base_color]\n        return "rgb" + str(tuple(segment_color))'
+src = src.replace(old_b, new_b)
+src = src.replace("self.base_opacity = 0.1", "self.base_opacity = 0.3")
+f.write_text(src)
+EOF
+
+# rmapi binary
+COPY backup/rmapi /usr/local/bin/rmapi
+RUN chmod +x /usr/local/bin/rmapi
+
+# Skripte
+COPY scripts/backup-official-cloud.sh /usr/local/bin/remarkable-backup.sh
+COPY scripts/convert-to-pdf.sh /usr/local/bin/remarkable-convert.sh
+COPY scripts/merge-annotations.py /usr/local/bin/remarkable-merge.py
+RUN chmod +x /usr/local/bin/remarkable-merge.py
+RUN chmod +x /usr/local/bin/remarkable-backup.sh /usr/local/bin/remarkable-convert.sh
+
+# Web-UI
+COPY web/ /app/
+
+# Entrypoint
+COPY entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+
+EXPOSE 8080
+ENTRYPOINT ["/entrypoint.sh"]