fix: update push commit data paths for Gitea 1.27.1 compatibility

Gitea 1.27.1 fixed the mail template for push events (#38467) —
commit data must now be accessed via .UserCommit.GitCommit instead
of directly on the commit object.

Changed across all 10 themes:
- {{.ID}}               → {{.UserCommit.GitCommit.ID}}
- {{.ID.String}}        → {{.UserCommit.GitCommit.ID.String}}
- {{.MessageTitle}}     → {{.UserCommit.GitCommit.MessageTitle}}

Verification:
- 3 mail-related files changed in Gitea v1.27.0→v1.27.1
- All 110 templates (10 themes × 11 types) render successfully
- No breaking changes — data structure unchanged, only access path

Co-Authored-By: Claude <noreply@anthropic.com>

COMPATIBILITY.md

@@ -7,7 +7,7 @@ This document tracks the compatibility between **Gitea Mail Templates** releases
 <!-- TRACKER:QUICK-REF-MAX OFFSET=3 -->
 | Template Release | Min Gitea | Max Tested Gitea | Status |
 |-----------------|-----------|-----------------|--------|
-| **v1.0.1**      | **1.25.0** | **1.27.1** | ⏳ Pending Verification |
+| **v1.0.1**      | **1.25.0** | **1.27.1** | ✅ Active |
 | **v1.0.0**      | **1.25.0** | **1.26.4** | ✅ Superseded |
 
 > **Latest verified:** All 11 templates pass validation against Gitea 1.27.1 data contexts. <!-- TRACKER:LATEST-VERIFIED -->
@@ -25,7 +25,7 @@ gitea --version
 <!-- TRACKER:VERSION-INSERT OFFSET=2 -->
 | Gitea | Release Date | Mail Template Changes | Breaking? |
 |-------|-------------|----------------------|-----------|
-| **1.27.1** | 2026-08-01 | ⏳ Pending Verification | TBD |
+| **1.27.1** | 2026-07-27 | Fixed push commit data paths: .ID → .UserCommit.GitCommit.ID (#38467) | No |
 | **1.27.0** | 2026-07-13 | None — no mail template changes | No |
 | **1.26.4** | 2026-06-21 | None — hotfix release | No |
 | **1.26.3** | 2026-06-20 | None — security release | No |