refactor(ci): use marker comments instead of regex for tracker workflow

Add TRACKER: HTML comment markers to COMPATIBILITY.md, README.md, and
all 5 translation READMEs. Rewrite gitea-tracker.yml to use grep -n
for precise line-based insertion and sed line-address editing.

Markers introduced:
- TRACKER:QUICK-REF-MAX  — Quick Reference max tested version
- TRACKER:VERSION-INSERT — Version History row insertion point
- TRACKER:LATEST-VERIFIED — latest verified note version
- TRACKER:BADGE — shields.io badge version
- TRACKER:LATEST-TESTED — latest tested version in READMEs

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

README.md

@@ -2,7 +2,7 @@
 
 A curated collection of professionally designed, audience-driven email templates for self-hosted [Gitea](https://about.gitea.com) instances.
 
-[![Gitea](https://img.shields.io/badge/Gitea-1.25+%20%7C%201.26.4%20tested-blue)](COMPATIBILITY.md)
+[![Gitea](https://img.shields.io/badge/Gitea-1.25+%20%7C%201.26.4%20tested-blue)](COMPATIBILITY.md) <!-- TRACKER:BADGE -->
 
 > **110 template files — 10 visual styles, 11 email types each**
 
@@ -164,7 +164,7 @@ gitea-mail-templates/
 ## Compatibility
 
 - **Gitea 1.25+** — matches the refactored mail template directory structure (v1.25)
-- **Latest tested:** Gitea 1.26.4
+- **Latest tested:** Gitea 1.26.4 <!-- TRACKER:LATEST-TESTED -->
 - 100% variable-compatible with official Gitea templates — see [COMPATIBILITY.md](COMPATIBILITY.md) for the full matrix
 - Uses only built-in Gitea template functions and official translation keys
 - No custom template functions or locale patches required