docs: add Gitea milestone tracking instructions to all phase docs

Each phase doc now includes:
- Milestone Tracking section linking to the corresponding Gitea milestone
- Checklist item in Completion Criteria to close the milestone
- Phase 7 also closes the Final: Porting Complete milestone (ID 8)

docs/plans/phases/phase-5-mapping-verification.md

@@ -16,6 +16,10 @@ Confirm zero unmapped items, validate all N/A justifications, enforce naming con
 - **Go source code** is located in the `golang/` folder (specifically `golang/nats-server/`)
 - **.NET ported version** is located in the `dotnet/` folder
 
+## Milestone Tracking
+
+This phase corresponds to **Milestone 5** in [Gitea](https://gitea.dohertylan.com/dohertj2/natsnet/milestone/5). When starting this phase, verify the milestone is open. Assign relevant issues to this milestone as work progresses.
+
 ## Steps
 
 ### Step 1: Confirm zero unmapped items
@@ -191,6 +195,14 @@ dotnet run --project tools/NatsNet.PortTracker -- feature map <id> \
 - All tests target the correct test project
 - `phase check 5` passes with no errors
 - Mapping report exported and reviewed
+- [ ] Close the Phase 5 milestone in Gitea:
+  ```bash
+  curl -s -X PATCH "https://gitea.dohertylan.com/api/v1/repos/dohertj2/natsnet/milestones/5" \
+    -H "Content-Type: application/json" \
+    -H "Authorization: token $GITEA_TOKEN" \
+    -d '{"state":"closed"}'
+  ```
+  Or close it via the Gitea web UI at https://gitea.dohertylan.com/dohertj2/natsnet/milestone/5
 
 ## Related Documentation