Merge branch 'ralph/dashboard-realtime' — SSE realtime + story rollback

Server-Sent Events (TODO P3):
- GET /api/ralph/stream — signature-based change detection (poll FS 2s, emit
  doar la diff), heartbeat 30s, X-Accel-Buffering:no
- HTTPServer → ThreadingHTTPServer (altfel SSE blochează toate endpoint-urile)
- ralph.html: EventSource cu fallback permanent la polling 5s când CLOSED.
  Badge: 🟢 Live / ⏱ Polling / Offline

Story rollback (TODO P3):
- POST /api/ralph/<slug>/rollback — git revert --no-edit HEAD; fallback
  git reset --hard HEAD~1 doar la conflict
- Decrementează passes pe ultima story complete; clears failed/blocked/retries
  (atomic temp+rename)
- Slug strict regex ^[A-Za-z0-9_-]{1,64}$ + reject path traversal explicit
- Buton ↩️ pe card-uri running; confirm dialog înainte de execuție
- Response: {success, message, reverted_commit, story_reverted, method}

Tests: 39/39 pe test_dashboard_ralph_endpoint (era 19; +20 cazuri noi).

# Conflicts:
#	dashboard/api.py
#	dashboard/handlers/ralph.py

dashboard/api.py

@@ -7,7 +7,7 @@ server bootstrap.
 """
 import json
 import sys
-from http.server import HTTPServer, SimpleHTTPRequestHandler
+from http.server import SimpleHTTPRequestHandler, ThreadingHTTPServer
 from pathlib import Path
 
 # Make dashboard/ importable for the handler submodules (constants,
@@ -165,6 +165,8 @@ class TaskBoardHandler(
             self.handle_ralph_status()
         elif self.path == '/api/ralph/usage' or self.path.startswith('/api/ralph/usage?'):
             self.handle_ralph_usage()
+        elif self.path == '/api/ralph/stream' or self.path.startswith('/api/ralph/stream?'):
+            self.handle_ralph_stream()
         elif self.path.startswith('/api/ralph/'):
             # /api/ralph/<slug>/log or /api/ralph/<slug>/prd
             parts = self.path.split('?', 1)[0].split('/')
@@ -239,11 +241,18 @@ class TaskBoardHandler(
             self.handle_eco_git_commit()
         elif self.path == '/api/eco/restart-taskboard':
             self.handle_eco_restart_taskboard()
-        elif self.path.startswith('/api/ralph/') and self.path.endswith('/stop'):
+        elif self.path.startswith('/api/ralph/'):
+            # /api/ralph/<slug>/{stop,rollback}
             parts = self.path.split('?', 1)[0].split('/')
             if len(parts) >= 5:
                 slug = parts[3]
-                self.handle_ralph_stop(slug)
+                action = parts[4]
+                if action == 'stop':
+                    self.handle_ralph_stop(slug)
+                elif action == 'rollback':
+                    self.handle_ralph_rollback(slug)
+                else:
+                    self.send_error(404)
             else:
                 self.send_error(404)
         else:
@@ -270,5 +279,8 @@ if __name__ == '__main__':
     os.chdir(KANBAN_DIR)
 
     print(f"Starting Echo Task Board API on port {port}")
-    httpd = HTTPServer(('0.0.0.0', port), TaskBoardHandler)
+    # ThreadingHTTPServer permite SSE long-lived (/api/ralph/stream) fără să
+    # blocheze celelalte request-uri.
+    httpd = ThreadingHTTPServer(('0.0.0.0', port), TaskBoardHandler)
+    httpd.daemon_threads = True
     httpd.serve_forever()