Add automatic slide partner logos and refresh LaTeX devcontainer

Slides/README.md

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+# Slides
+
+Compile `slides.tex` with LuaLaTeX (and Biber for references).
+
+## Partner and funding logos
+
+Enable partners in the preamble, in the desired display order:
+
+```latex
+\partner{labsticc}\partner{ubo}\partner{aid}\partner{ifremer}
+```
+
+Logos for the following partners are included in `img/partners/`:
+
+| Identifier | Partner |
+| --- | --- |
+| `labsticc` | Lab-STICC |
+| `ubo` | Université de Bretagne Occidentale |
+| `ensta` | ENSTA, Institut Polytechnique de Paris |
+| `aid` | Agence de l'innovation de défense |
+| `ifremer` | Ifremer |
+| `lip6` | Laboratoire d'informatique de Sorbonne Université |
+| `sorbonne` | Sorbonne Université |
+| `academia-sinica` | Academia Sinica |
+| `taipei` | University of Taipei |
+
+For example, enable the additional four with:
+
+```latex
+\partner{lip6}\partner{sorbonne}\partner{academia-sinica}\partner{taipei}
+```
+
+Enable ENSTA with `\partner{ensta}`.
+
+Asset sources are recorded in [`img/partners/README.md`](img/partners/README.md).
+Add other individual logos in `img/partners/`, named after their identifier:
+
+```text
+img/partners/labsticc.png
+img/partners/ubo.png
+img/partners/aid.png
+img/partners/ifremer.png
+```
+
+PNG, PDF, JPG and JPEG are supported, searched in that order. All nine bundled
+assets are transparent PNGs. Prefer high-resolution transparent PNGs or vector
+PDFs, tightly cropped to the artwork;
+embedded white space counts towards a logo's dimensions. SVGs should first be
+exported to PDF. The existing `img/logos.png` is a combined UBO/Lab-STICC image,
+not two independently selectable logos.
+
+For other file locations or identifiers, register a path (with or without its
+extension) and then enable the partner:
+
+```latex
+\declarepartner{my-funder}{img/custom-funder.pdf}
+\partner{my-funder}
+```
+
+The title page places the logos at the bottom right, inside the theme's margins.
+Column count, logo sizes, cell sizes, spacing and row wrapping are computed from
+the number of available logos, their aspect ratios, the column width and the
+slide height. Logos have equal bounding-box area for comparable visual weight:
+wide wordmarks are shorter than square seals, rather than dominating the block.
+Aspect ratios are preserved; logos are centred within evenly spaced grid cells.
+The final row is right-aligned and stays within a bounded title-page area.
+Repeated selections are ignored. Missing files produce warnings and are skipped,
+without inserting placeholder logos. Partners do not appear on ordinary slides.
+
+With no partners selected, the existing `\titlegraphic{...}` is still used.
+When partners are selected, they replace the legacy title graphic.
+
+### Additional information
+
+No additional logo files are needed for the nine included partners. If a funder
+requires a specific logo variant, minimum size, ordering or acknowledgement text,
+provide those project-specific requirements. No manual layout dimensions are needed.