Document wait endpoint exception and mandatory duration logging

[TaprootFreakAI]

EN:
Exempt wait endpoints, including long polling, from the 100ms response deadline and require logging the actual waiting duration of every individual request. All other quality requirements remain applicable.

DE:
Wait-Endpunkte einschliesslich Long-Polling von der 100-ms-Antwortfrist ausnehmen und die tatsächliche Wartezeit jedes einzelnen Aufrufs protokollieren. Alle übrigen Qualitätsanforderungen gelten weiterhin.

Details

Clarifies CONTRIBUTING.md, README.md and REVIEW.md consistently: a wait request may remain open for its intended wait, every individual actual waiting duration must be logged, and duration alone must not cause a 100ms cutoff or review/CI failure. The exception does not authorize forwarding known endpoints.

Documentation only, as explicitly requested. No runtime, route, catalog, test or deployment changes; this PR does not claim wait handling or duration logging is implemented.

Replaces #17 with the identical final tree in one signed commit, published through the author's fork. No published commits were rewritten. #18 was an unsuccessful redundant publication attempt and is closed.

Review scope: existing unidentified frontend E2E catalog entries remain (/ , /version, swagger aliases, /v1/statistic, /v1/coin, /v1/setting, /v1/bank, /v1/app). They are reported under REVIEW.md item 11. The user's explicit documentation-only instruction excludes unrelated implementation and E2E additions; no endpoint is added or changed by this PR, and no claim is made that those existing gaps are resolved.

Validation: signed clean commit, identical tree to #17, git diff --check, and required hosted test suite on this PR's final head. Final results are recorded in the self-review; no independent approval is claimed.

[TaprootFreakAI]

Final self-review on eabdd9a (not an independent approval).

• CONTRIBUTING.md and REVIEW.md checked: English public documentation, EN/DE PR summary, correct develop base, no private repository or unlisted endpoint named, documentation-only scope.
• GitHub confirms the sole commit is verified (reason: valid). Local signature verification passes; working tree is clean. Published history was not rewritten.
• All three documentation files state the wait-endpoint exception and mandatory actual-duration logging for every individual wait request. Other quality requirements, including no forwarding of known routes, remain applicable.
• Final tree is identical to the reviewed tree of #17. Whitespace check passes. No runtime, endpoint, catalog, workflow, image or environment change; corresponding behavior-test and frontend-E2E-change gates are not triggered.
• Required hosted test job succeeded on this final head: https://github.com/DFXswiss/front-api/actions/runs/34037964096/job/101499401758 . Mergeable, no open review threads.
• Written scoped review decision under REVIEW.md item 11: accept deferral of the pre-existing unidentified E2E rows listed in the PR body for this documentation-only PR, consistent with the user's express concept-only scope. This decision applies only to this PR, does not resolve those gaps and does not authorize any endpoint implementation without its required E2E coverage.

Ready for review. Human merge remains outstanding.