Use or remove watchdog production dependency

[electron-rare]

File: apps/api/pyproject.toml:13

watchdog>=5.0.0 is declared in [project.dependencies] (production deps, not dev) but never imported anywhere in apps/api/src/. Inflates the production container image unnecessarily.

Options:

• (a) Remove from dependencies
• (b) Use it to replace the 500ms polling in tail_log_sse (more efficient, was likely the original intent)

(b) is the cleaner long-term fix.