implemented 07-server-mode.md: added server profile with REST API for builds, artifacts, live logs, and control tokens; lifecycle management for watcher; controller and service tests

src/main/kotlin/de/hoennig/gittally/server/WatcherApiController.kt

@@ -0,0 +1,15 @@
+package de.hoennig.gittally.server
+
+import de.hoennig.gittally.watcher.Watcher
+import de.hoennig.gittally.watcher.WatcherState
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.RestController
+
+@RestController
+class WatcherApiController(
+    private val watcher: Watcher,
+) {
+    /** Watcher health: whether the loop runs, last poll, last fetch/poll error. */
+    @GetMapping("/api/watcher")
+    fun watcher(): WatcherState = watcher.state()
+}