feat(ui): 3-tab UI per spec — admin dashboard + date filter, personal dashboard, training w/ difficulty, settings profile

Tab 1 Admin overview (/): aggregate stats + DATE FILTER (?from&to), hardest personas,
admin quick actions (Users / + Add product).
Tab 2 My dashboard (/my/board): per-user win/lose/session summary (works for admin too).
Tab 3 Training (/training): product list w/ status + persona count; admins see all groups
(draft->analyze/edit), trainees see ready->personas; persona list shows DIFFICULTY (1-5
stars); admins get a Manage-personas button.
Settings (/settings): profile (name/email) via new PATCH /api/auth/profile + change
password + language.
Backend: analytics date filter; profile endpoint; /api/me/board + /api/chat/sessions
opened to any authed user.
Rebuilt frontend/dist.

backend/app/api/analytics_routes.py

@@ -1,7 +1,8 @@
-"""Admin analytics: aggregate trainee results."""
+"""Admin analytics: aggregate trainee results (supports date-range filter)."""
 from __future__ import annotations
 
-from flask import Blueprint, jsonify
+import datetime
+from flask import Blueprint, jsonify, request
 
 from .helpers import ApiError, current_user, require_auth, require_roles
 
@@ -18,22 +19,51 @@ def _stores():
     }
 
 
+def _parse_date_iso(value: str | None, *, end: bool = False) -> str | None:
+    """Parse a YYYY-MM-DD into an ISO datetime bound for created_at filtering."""
+    if not value:
+        return None
+    try:
+        d = datetime.date.fromisoformat(value.strip())
+    except ValueError:
+        return None
+    if end:
+        # end-of-day bound (inclusive)
+        return datetime.datetime.combine(d, datetime.time(23, 59, 59, 999999), tzinfo=datetime.timezone.utc).isoformat()
+    return datetime.datetime.combine(d, datetime.time(0, 0, 0), tzinfo=datetime.timezone.utc).isoformat()
+
+
 @analytics_bp.get("")
 @require_auth
 @require_roles("admin")
 def analytics():
     s = _stores()
     actor = current_user()
+
+    # Date filter (optional) from ?from=YYYY-MM-DD&to=YYYY-MM-DD on created_at
+    date_from = _parse_date_iso(request.args.get("from"))
+    date_to = _parse_date_iso(request.args.get("to"), end=True)
+
+    def _in_window(sess) -> bool:
+        created = (sess.get("created_at") or "")[:19]
+        if not created:
+            return True
+        if date_from and created < date_from[:19]:
+            return False
+        if date_to and created > date_to[:19]:
+            return False
+        return True
+
     if actor.get("role") == "super_admin":
-        sessions = s["sessions"].sessions.all()
         users = s["users"].list_users()
+        sessions = [x for x in s["sessions"].sessions.all() if _in_window(x)]
     else:
         org_id = actor.get("org_id")
-        # users in this org
         users = s["users"].list_users(org_id=org_id)
         user_ids = {u["id"] for u in users}
         sessions = [
-            x for x in s["sessions"].sessions.all() if x.get("user_id") in user_ids
+            x for x in s["sessions"].sessions.all()
+            if x.get("user_id") in user_ids and _in_window(x)
         ]
 
     overall = {