fix(flask): wrap wsgi_app call in try/except to prevent active_requests gauge leak (#4433)

* fix(flask): wrap wsgi_app call in try/except to prevent active_requests gauge leak

If wsgi_app() raises an uncaught exception, the active_requests_counter
decrement at the end of _wrapped_app was never reached, causing the gauge
to permanently read high. Kubernetes HPA and similar systems would see
phantom load.

Add a bare try/except that decrements the counter and re-raises on
exception, matching the pattern already used in the WSGI instrumentation.

Fixes #4431

Signed-off-by: alliasgher <alliasgher123@gmail.com>

* fix(flask): use try/finally for active_requests decrement per review

Signed-off-by: alliasgher <alliasgher123@gmail.com>

* fix(flask): add regression test for active_requests gauge leak on error

Signed-off-by: alliasgher <alliasgher123@gmail.com>

* chore: add CHANGELOG entry for #4433

Signed-off-by: Ali <alliasgher123@gmail.com>

* test: flatten nested blocks to satisfy pylint R1702

Signed-off-by: Ali <alliasgher123@gmail.com>

* chore: fix 5 pre-existing broken links in CHANGELOG.md

The check-links workflow fails on any PR that touches CHANGELOG.md
because the full file is scanned and five historical entries contain
broken URLs:

- #1670 and #227 entries have a stray `]` inside the URL.
- The #1033 entry is missing the `/` between the org and repo in the URL.
- The `aws.ecs.*` spec link points to the old path in
  opentelemetry-specification; the content has since moved to the
  semantic-conventions repo.
- The 1.12.0rc2-0.32b0 release tag does not exist on
  opentelemetry-python; drop the link, keep the heading text.

Signed-off-by: Ali <alliasgher123@gmail.com>

* style: apply ruff format to flask regression test

Signed-off-by: Ali <alliasgher123@gmail.com>

* chore: drop unrelated CHANGELOG cleanup from this PR

Per @MikeGoldsmith's review, the changelog broken-link cleanup that was
folded into this branch via bb17ad0 should not be mixed with the flask
fix. Reset CHANGELOG.md to upstream/main and re-add only this PR's
entry. Most of the broken links from bb17ad0 have already been fixed
on main independently, so no separate cleanup PR is needed.

Signed-off-by: Ali <alliasgher123@gmail.com>

* add changelog

Signed-off-by: emdneto <9735060+emdneto@users.noreply.github.com>

---------

Signed-off-by: alliasgher <alliasgher123@gmail.com>
Signed-off-by: Ali <alliasgher123@gmail.com>
Signed-off-by: emdneto <9735060+emdneto@users.noreply.github.com>
Co-authored-by: Emídio Neto <9735060+emdneto@users.noreply.github.com>