TF-4384 Add ADR-0074 Resolve label refresh 404 by introducing explicit labelId (#4387)

docs/adr/0074-fix-label-refresh-404-with-explicit-label-id-routing.md

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+# 0074 - Fix 404 on Label Refresh by Introducing Explicit `labelId` in Web Routing
+
+Date: 2026-03-18
+
+## Status
+
+Proposed
+
+## Context
+
+Refreshing a label view on web results in a 404 error because label IDs are incorrectly interpreted as `mailboxId` from the URL.
+
+## Decision
+
+Introduce an explicit `labelId` query parameter to distinguish labels from mailboxes in routing.
+
+* Mailbox: `/dashboard?context=<mailboxId>`
+* Label: `/dashboard?labelId=<labelId>`
+
+## Consequences
+
+* ✅ Fixes 404 on refresh
+* ✅ Enables correct deep linking and bookmarking
+* ⚠️ Requires updating routing logic and URL generation
+* ⚠️ Legacy URLs must be handled via fallback logic