docs: cover the bulk media actions rework and Tracearr server binding

[enoch85]

Closes #145. Doc updates for the drift between v3.22.0 and Maintainerr HEAD, confirmed against the upstream diffs rather than the report summary.

What was added

File	Change	Upstream
docs/Collections.md	Rewrote the Add / Remove Media modal section: all three grids offer the same actions, a collection page preselects its collection instead of locking the picker, Remove from all collections folded into Remove from collection + All collections, search results can be added, Plex library scoping and the refused cross-library add, per-item failure reasons	Maintainerr#3453
docs/Collections.md	Excluding also drops the selection from the collections it covers, and an exclusion waits up to 30s for a running job before it is refused	Maintainerr#3453
docs/Collections.md	The collection handler skips a member an exclusion covers, manually added ones included	Maintainerr#3453
docs/Configuration.md	Tracearr server field is only shown when there is a real choice; Maintainerr picks the server that tracks your media server, refuses a mismatched one, re-checks on a media-server re-point, and makes rule values unavailable when the server cannot be confirmed	Maintainerr#3446, Maintainerr#3450
docs/API.md	409 on the two exclusion-add routes; server_id optional on POST /api/settings/tracearr; corrected the Tracearr test endpoint description	Maintainerr#3453, Maintainerr#3446
static/openapi-spec/maintainerr_api_specs.yaml	409 on /api/rules/exclusion and /api/rules/exclusions/bulk, server_id dropped from TracearrSetting.required	same as above
AGENTS.md, .github/copilot-instructions.md	Standing rules for docs drift PRs, requested separately by the maintainer	n/a

Already covered by prior PRs

Drift item	Where
Tracearr integration, rule keys, settings endpoints	#131, #140
Bulk exclusions and Studios rules	#133
Exclusion badge and Test Media placement	#143
Glossary parity (205/205 keys)	already in sync, nothing to do

Skipped as not user-facing: the batched collection-size and maintenance-sweep reads (Maintainerr#3449, Maintainerr#3452), the production-build blur fix, and the dropped Tracearr-only warning banner, which had no doc text.