Sanitize codebase, reorganize docs, and add missing deploy files

Remove dead code identified in docs/SANITIZATION-REVIEW.md:
- app/blueprints/content_old.py and app/blueprints/playlist.py
- app/models/group.py, app/utils/nginx_config_reader.py
- orphaned templates (content_list, edit_content, upload_content,
  player_page) and the related group/Template references

Result: 6 blueprints, 82 routes, no dead modules or orphan templates.

Add files that deploy.sh and docker-entrypoint.sh already require but
which were never tracked:
- https_manager.py       (referenced by deploy.sh, migrate_network.sh,
                          docker-entrypoint.sh)
- Caddyfile.example      (seeded by deploy.sh; its absence aborts deploy)

Relocate generated Graphify artifacts from graphify-out/ to
docs/graphify-out/ (110 files, no content change) and archive the
superseded docs under docs/.

Ignore hygiene:
- ignore ad-hoc .env backups (.env.bak*) — they contain live secrets
- keep the pre-sanitization snapshots (docs/legacy code/,
  docs/old_code_documentation/) on disk but out of the repo

Fix .env.example: drop a duplicated config block, genericize the
hardcoded host IP, and document HOSTNAME_INTERNAL.

docs/graphify-out/wiki/Community_12.md

@@ -0,0 +1,32 @@
+# Community 12
+
+> 8 nodes · cohesion 0.29
+
+## Key Concepts
+
+- [pptx_converter.py](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py#L1) (4 connections)
+- [cleanup_libreoffice_processes()](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py#L11) (3 connections)
+- [pptx_to_pdf_libreoffice()](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py#L20) (3 connections)
+- [validate_pptx_file()](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py#L86) (2 connections)
+- [PowerPoint to PDF converter using LibreOffice.](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py#L1) (1 connections)
+- [Clean up any hanging LibreOffice processes.](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py#L12) (1 connections)
+- [Convert PPTX to PDF using LibreOffice for highest quality.          This functio](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py#L21) (1 connections)
+- [Validate if file is a valid PowerPoint file.          Args:         filepath: Pa](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py#L87) (1 connections)
+
+## Relationships
+
+- No strong cross-community connections detected
+
+## Source Files
+
+- [/home/scheianu/digiserver-v2/app/utils/pptx_converter.py](file:///home/scheianu/digiserver-v2/app/utils/pptx_converter.py)
+
+## Audit Trail
+
+- EXTRACTED: 16 (100%)
+- INFERRED: 0 (0%)
+- AMBIGUOUS: 0 (0%)
+
+---
+
+*Part of the graphify knowledge wiki. See [[index]] to navigate.*