Improve page/tab titles across web projects to distinguish instances

[thusser]

Summary

Browser tab titles for pyobs web projects (robotic-backend, web-client, archive, etc.) are hard to tell apart when several are open at once. Need a better naming scheme so tabs are distinguishable.

Notes

• Should apply consistently across all web projects.
• Consider including project name + distinguishing info (e.g. instance/site name) in the title.

[thusser]

Surveyed all four Django projects:

• pyobs-archive: single page, nothing to distinguish between tabs of the same app.
• pyobs-pipeline, pyobs-web-admin: already had proper per-page dynamic titles (e.g. {{ pipeline.name }} — pyobs Pipeline, {{ module_name }} — pyobs Web Admin).
• pyobs-robotic-backend: task_detail.html's browser tab title was static ("Task — pyobs Robotic") regardless of which task was open. Fixed — document.title now updates with the task's name (or id/clone-source/"New task") once loaded.

Also gave each project a distinct favicon + matching login-page icon while in there, so tabs are distinguishable by icon as well as title (archive=blue archive box, pipeline=purple diagram, robotic-backend=teal robot, web-admin=orange gear) — those were previously either missing or using a dead bi-telescope class that isn't a real Bootstrap Icons glyph.

pyobs-web-client not included (deferred along with its theme-switcher and logo work, see #749/#751).