Feat: Rebrand, allow for custom brands

[rikled]

These PRs replace some more onlyoffice logos, replace onlyoffice orange theme color by nextcloud blue theme color and add the ability to integrate custom brands.

depends on Euro-Office/server#24 Euro-Office/document-server-integration#9 Euro-Office/document-server-package#9

[chrip]

Great work on the rebranding infrastructure. This lays a solid foundation for custom branding. Here are some observations:

Positive:

• Clean separation of branding variables (COMPANY_NAME, COMPANY_NAME_LOW, PRODUCT_NAME, PRODUCT_NAME_LOW) in docker-bake.hcl
• Using regex_replace(lower(...)) for slugification is a good touch
• Supervisor configs now use environment variables instead of hardcoded paths, which is much more maintainable

Suggestions:

1. bundle.bake.Dockerfile — sed substitutions on config JSON files (lines 56-61, 80-85):
   Using sed to replace strings in JSON files at build time is fragile. If any config file contains the substring euro-office or documentserver in a value (not a key/path), it will be incorrectly replaced. Consider using jq or a more targeted replacement strategy for JSON files.

2. orchestrated.bake.Dockerfile — hardcoded fallback value (line 9):
   ARG COMPANY_NAME_LOW=euro-office hardcodes the fallback. This means builds that don't explicitly pass COMPANY_NAME_LOW will still produce euro-office branded images. Is this intentional? If the goal is full rebranding, the default should perhaps be empty or a generic placeholder.

3. standalone.bake.Dockerfile — debconf selections (lines 40-45):
   The debconf lines still reference eurooffice for the PostgreSQL user/db name. These should either be parameterized or documented as requiring manual override for custom brands.

4. entrypoint.sh — string interpolation without quoting (lines 4-5, 33, 44-46):
   Variables like ${EO_ROOT}-example and ${EO_CONF}-example are used without quotes. If paths contain spaces (possible with custom COMPANY_NAME), this could break. Recommend quoting: "${EO_ROOT}-example".

5. ds-example.conf (lines 8-9):
   %(ENV_EO_ROOT)s-example and %(ENV_EO_CONF)s-example — using -example suffix assumes the example app always lives under the same root. This works for the current naming scheme but may be confusing for brands with different naming conventions. Consider an explicit EXAMPLE_SUFFIX variable.

6. Missing newline at EOF — mariadb:$MARIADB_VERSION AS db-mariadb section in orchestrated.bake.Dockerfile has no trailing newline (git diff shows \ No newline at end of file). Minor but worth fixing for cleanliness.

Overall: Solid foundation for the rebranding effort. Once the JSON sed fragility and unquoted variable usage are addressed, this should be ready to merge.