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superseded docs under docs/.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.

migrations/migrate_player_user_global.py

@@ -1,4 +1,13 @@
-"""Migrate player_user table to remove player_id and make user_code unique globally."""
+"""Migrate player_user table to remove player_id and make user_code unique globally.
+
+Idempotent and data-preserving: the table is only rebuilt when the legacy
+``player_id`` column is actually present. Existing code/name pairs are carried
+over into the new schema, and on a fresh or already-migrated database this
+script is a no-op.
+
+The rebuild uses a temporary table rather than a bare ``DROP TABLE`` so that
+user data is never lost.
+"""
 import sys
 sys.path.insert(0, '/app')
 
@@ -10,15 +19,51 @@ app = create_app('production')
 
 with app.app_context():
     print("Migrating player_user table...")
-    
-    # Drop existing table and recreate with new schema
-    db.session.execute(text('DROP TABLE IF EXISTS player_user'))
-    db.session.commit()
-    
-    # Create new table
-    db.create_all()
-    
+
+    inspector = db.inspect(db.engine)
+
+    if 'player_user' not in inspector.get_table_names():
+        # Fresh database — just create the current schema.
+        db.create_all()
+        print("✓ player_user table created with current schema.")
+        sys.exit(0)
+
+    columns = [col['name'] for col in inspector.get_columns('player_user')]
+
+    if 'player_id' not in columns:
+        # Already migrated — running the migration again must not destroy data.
+        db.create_all()
+        print("✓ player_user table already migrated, skipping.")
+        sys.exit(0)
+
+    # Legacy schema detected: rebuild it, preserving user_code/user_name.
+    print("  Legacy schema detected (player_id present) — rebuilding...")
+    with db.engine.connect() as conn:
+        conn.execute(text(
+            'CREATE TABLE player_user_new ('
+            '  id INTEGER PRIMARY KEY,'
+            '  user_code VARCHAR(255) NOT NULL UNIQUE,'
+            '  user_name VARCHAR(255),'
+            '  created_at DATETIME NOT NULL,'
+            '  updated_at DATETIME NOT NULL'
+            ')'
+        ))
+
+        # De-duplicate on user_code (the new schema makes it globally unique).
+        conn.execute(text(
+            'INSERT OR IGNORE INTO player_user_new '
+            '(id, user_code, user_name, created_at, updated_at) '
+            'SELECT id, user_code, user_name, created_at, updated_at '
+            'FROM player_user '
+            'WHERE user_code IS NOT NULL'
+        ))
+
+        conn.execute(text('DROP TABLE player_user'))
+        conn.execute(text('ALTER TABLE player_user_new RENAME TO player_user'))
+        conn.commit()
+
     print("✓ player_user table migrated successfully!")
     print("  - Removed player_id foreign key")
     print("  - Made user_code unique globally")
     print("  - user_name is now nullable")
+    print("  - Existing user_code/user_name rows preserved")