feat(notifications): direct BRD + Plane links in approve ping (ORCH-017)

notify_approve_requested now embeds two HTML <a> links into the single
notifying approve-gate message: a Gitea branch-view link to 01-brd.md and a
Plane issue browser link. Adds ORCH_PLANE_WEB_URL (external Plane web URL,
fallback to plane_api_url) with a loopback-guard that omits the Plane link
when the resolved base is localhost/empty (no broken localhost URLs in prod).

Each link is built independently and omitted on missing data; the message and
the "flip to Approved" call to action are always sent as exactly one ping. The
shared send_telegram helper is left untouched (min blast radius for the
self-hosting prod container). Dynamic labels are html.escaped; parse_mode=HTML
preserved. QG registry / stages / approve handler unchanged.

Docs updated in-PR: CHANGELOG, .env.example, INFRA env map.
Tests: test_notify_approve_links.py, test_analysis_approve_flow_links.py.

Refs: ORCH-017
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.env.example

@@ -1,4 +1,8 @@
 ORCH_PLANE_API_URL=http://plane-app-api-1:8000
+# External (browser) web URL of Plane for clickable issue links in notifications
+# (ORCH-017). Falls back to ORCH_PLANE_API_URL; a loopback fallback is treated as
+# "no web URL" and the Plane link is omitted. Example: https://plane.example.org
+ORCH_PLANE_WEB_URL=
 ORCH_PLANE_API_TOKEN=
 ORCH_PLANE_WORKSPACE_SLUG=
 ORCH_PLANE_WEBHOOK_SECRET=