feat(devops): configure desktop packaging and introduce semantic versioning

- Added `nativeDistributions` for Linux (.deb), Windows (.msi), and macOS (.dmg) in `build.gradle.kts` with platform-specific settings, embedded JRE, and JVM-args.
- Implemented centralized semantic versioning via `version.properties` as the single source of truth, applying it across all builds.
- Introduced CI/CD release workflow (`.gitea/workflows/release.yml`) for auto-tagging, artifact builds, and release summaries.
- Created `CHANGELOG.md` following Keep-a-Changelog format for tracking changes.
- Documented icon requirements and packaging steps in `ICONS_PLACEHOLDER.md`.
- Updated DevOps roadmap to reflect completed Sprint C-1 and C-2 tasks.

Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>

build.gradle.kts

@@ -38,9 +38,22 @@ plugins {
 // ###                  ALLPROJECTS CONFIGURATION                 ###
 // ##################################################################
 
+// ---------------------------------------------------------------
+// Zentrale Versionierung — liest version.properties (SemVer)
+// ---------------------------------------------------------------
+val versionProps =
+  java.util.Properties().also { props ->
+    rootProject.file("version.properties").inputStream().use { props.load(it) }
+  }
+val vMajor = versionProps.getProperty("VERSION_MAJOR", "1")
+val vMinor = versionProps.getProperty("VERSION_MINOR", "0")
+val vPatch = versionProps.getProperty("VERSION_PATCH", "0")
+val vQualifier = versionProps.getProperty("VERSION_QUALIFIER", "").trim()
+val semVer = if (vQualifier.isBlank()) "$vMajor.$vMinor.$vPatch" else "$vMajor.$vMinor.$vPatch-$vQualifier"
+
 allprojects {
   group = "at.mocode"
-  version = "1.0.0-SNAPSHOT"
+  version = semVer
 }
 
 subprojects {