Add groups with shared goals, objectives and chat; drop the water tracker

Groups let people keep each other honest: create one or join with a
six-letter invite code. Each group has shared goals split into measurable
objectives (km, sessions, words) that every member logs toward, a
leaderboard of kept rate and streak with nudges, and a group chat where
check-ins and nudges appear as cards beside the talk. The open chat polls
for new messages.

Reached from a new Groups tab (Training moves into the day rail), a Home
"Your groups" rail that opens the chat, and a Group tile in the add sheet.
Mock mode seeds two groups, a joinable one and members who reply.

The water tracker is removed; it did not fit the app. Bottom sheets are
now square app-wide via the theme.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KhQh614DMeYoQEH9SoMRUw

frontend/lib/Grounded/about/external/initial/GroupGoalRequest.dart

@@ -0,0 +1,40 @@
+import 'ObjectiveDraft.dart';
+
+/// Creates a shared goal in a group, objectives and all.
+class GroupGoalRequest {
+  String groupId;
+
+  String? id;
+
+  String title;
+
+  String description;
+
+  String targetDate;
+
+  String colourHex;
+
+  List<ObjectiveDraft> objectives;
+
+  GroupGoalRequest({
+    this.groupId = "",
+    this.id,
+    this.title = "",
+    this.description = "",
+    this.targetDate = "",
+    this.colourHex = "",
+    List<ObjectiveDraft>? objectives,
+  }) : objectives = objectives ?? <ObjectiveDraft>[];
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = <String, dynamic>{};
+    data['groupId'] = groupId;
+    data['id'] = id;
+    data['title'] = title;
+    data['description'] = description;
+    data['targetDate'] = targetDate;
+    data['colourHex'] = colourHex;
+    data['objectives'] = objectives.map((item) => item.toJson()).toList();
+    return data;
+  }
+}

frontend/lib/Grounded/about/external/initial/GroupMessageRequest.dart

@@ -0,0 +1,18 @@
+/// Posts a message to a group chat.
+class GroupMessageRequest {
+  String groupId;
+
+  String body;
+
+  String kind;
+
+  GroupMessageRequest({this.groupId = "", this.body = "", this.kind = "Text"});
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = <String, dynamic>{};
+    data['groupId'] = groupId;
+    data['body'] = body;
+    data['kind'] = kind;
+    return data;
+  }
+}

frontend/lib/Grounded/about/external/initial/GroupRequest.dart

@@ -0,0 +1,21 @@
+/// Creates a group, or renames one when [id] is set.
+class GroupRequest {
+  String? id;
+
+  String name;
+
+  String description;
+
+  String colourHex;
+
+  GroupRequest({this.id, this.name = "", this.description = "", this.colourHex = ""});
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = <String, dynamic>{};
+    data['id'] = id;
+    data['name'] = name;
+    data['description'] = description;
+    data['colourHex'] = colourHex;
+    return data;
+  }
+}

frontend/lib/Grounded/about/external/initial/JoinGroupRequest.dart

@@ -0,0 +1,12 @@
+/// Joins a group by the code a friend shared.
+class JoinGroupRequest {
+  String inviteCode;
+
+  JoinGroupRequest({this.inviteCode = ""});
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = <String, dynamic>{};
+    data['inviteCode'] = inviteCode;
+    return data;
+  }
+}

frontend/lib/Grounded/about/external/initial/NudgeRequest.dart

@@ -0,0 +1,15 @@
+/// Nudges one member, or everyone when [memberId] is empty.
+class NudgeRequest {
+  String groupId;
+
+  String memberId;
+
+  NudgeRequest({this.groupId = "", this.memberId = ""});
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = <String, dynamic>{};
+    data['groupId'] = groupId;
+    data['memberId'] = memberId;
+    return data;
+  }
+}

frontend/lib/Grounded/about/external/initial/ObjectiveDraft.dart

@@ -0,0 +1,18 @@
+/// One objective as typed into the shared-goal editor.
+class ObjectiveDraft {
+  String title;
+
+  String unit;
+
+  double target;
+
+  ObjectiveDraft({this.title = "", this.unit = "", this.target = 0});
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = <String, dynamic>{};
+    data['title'] = title;
+    data['unit'] = unit;
+    data['target'] = target;
+    return data;
+  }
+}

frontend/lib/Grounded/about/external/initial/ObjectiveProgressRequest.dart

@@ -0,0 +1,24 @@
+/// Logs an amount against one objective of a shared goal.
+class ObjectiveProgressRequest {
+  String groupId;
+
+  String goalId;
+
+  String objectiveId;
+
+  double amount;
+
+  String note;
+
+  ObjectiveProgressRequest({this.groupId = "", this.goalId = "", this.objectiveId = "", this.amount = 0, this.note = ""});
+
+  Map<String, dynamic> toJson() {
+    final Map<String, dynamic> data = <String, dynamic>{};
+    data['groupId'] = groupId;
+    data['goalId'] = goalId;
+    data['objectiveId'] = objectiveId;
+    data['amount'] = amount;
+    data['note'] = note;
+    return data;
+  }
+}