feat(social): per-game friend request to disguised robots + lobby/stats/tile cosmetics

Functional: the in-game add-friend handshake aimed at an auto-match opponent who is
secretly a pooled robot now records the request per (game, seat) in a new
robot_friend_requests table -- never against the shared robot account -- mirroring the
robot_blocks pattern. The shared account stays out of friendships, the "requested" state
is pinned to the seat (not leaked across the player's other games), the robot ignores it,
and a background reaper drops the row 7 days after its game finishes. The outgoing-requests
list carries these per-game rows so the seat control stays disabled across reloads. No
withdraw UI, per owner decision.

Cosmetics:
- Lobby: an in-progress game tints the viewer's own score number green when leading or
  tied, red when trailing (reusing --ok/--danger); scores now render in seat-number order,
  matching the over-the-board scoreboard.
- Stats: the per-variant best move is laid out on two lines -- the variant label, then the
  score (right-aligned in its column) and the word tiles (left-aligned) below it.
- Dark theme: the played-tile background is a touch darker so a player-placed tile reads
  with more contrast (light theme unchanged).

Docs (ARCHITECTURE, FUNCTIONAL + _ru mirror, backend README, UI_DESIGN) updated in the
same change.

pkg/fbs/scrabblefb/OutgoingRequestList.go

@@ -61,8 +61,28 @@ func (rcv *OutgoingRequestList) RequestsLength() int {
 	return 0
 }
 
+func (rcv *OutgoingRequestList) Robots(obj *RobotFriendRef, j int) bool {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(6))
+	if o != 0 {
+		x := rcv._tab.Vector(o)
+		x += flatbuffers.UOffsetT(j) * 4
+		x = rcv._tab.Indirect(x)
+		obj.Init(rcv._tab.Bytes, x)
+		return true
+	}
+	return false
+}
+
+func (rcv *OutgoingRequestList) RobotsLength() int {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(6))
+	if o != 0 {
+		return rcv._tab.VectorLen(o)
+	}
+	return 0
+}
+
 func OutgoingRequestListStart(builder *flatbuffers.Builder) {
-	builder.StartObject(1)
+	builder.StartObject(2)
 }
 func OutgoingRequestListAddRequests(builder *flatbuffers.Builder, requests flatbuffers.UOffsetT) {
 	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(requests), 0)
@@ -70,6 +90,12 @@ func OutgoingRequestListAddRequests(builder *flatbuffers.Builder, requests flatb
 func OutgoingRequestListStartRequestsVector(builder *flatbuffers.Builder, numElems int) flatbuffers.UOffsetT {
 	return builder.StartVector(4, numElems, 4)
 }
+func OutgoingRequestListAddRobots(builder *flatbuffers.Builder, robots flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(1, flatbuffers.UOffsetT(robots), 0)
+}
+func OutgoingRequestListStartRobotsVector(builder *flatbuffers.Builder, numElems int) flatbuffers.UOffsetT {
+	return builder.StartVector(4, numElems, 4)
+}
 func OutgoingRequestListEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
 	return builder.EndObject()
 }

pkg/fbs/scrabblefb/RobotFriendRef.go

@@ -0,0 +1,97 @@
+// Code generated by the FlatBuffers compiler. DO NOT EDIT.
+
+package scrabblefb
+
+import (
+	flatbuffers "github.com/google/flatbuffers/go"
+)
+
+type RobotFriendRef struct {
+	_tab flatbuffers.Table
+}
+
+func GetRootAsRobotFriendRef(buf []byte, offset flatbuffers.UOffsetT) *RobotFriendRef {
+	n := flatbuffers.GetUOffsetT(buf[offset:])
+	x := &RobotFriendRef{}
+	x.Init(buf, n+offset)
+	return x
+}
+
+func FinishRobotFriendRefBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.Finish(offset)
+}
+
+func GetSizePrefixedRootAsRobotFriendRef(buf []byte, offset flatbuffers.UOffsetT) *RobotFriendRef {
+	n := flatbuffers.GetUOffsetT(buf[offset+flatbuffers.SizeUint32:])
+	x := &RobotFriendRef{}
+	x.Init(buf, n+offset+flatbuffers.SizeUint32)
+	return x
+}
+
+func FinishSizePrefixedRobotFriendRefBuffer(builder *flatbuffers.Builder, offset flatbuffers.UOffsetT) {
+	builder.FinishSizePrefixed(offset)
+}
+
+func (rcv *RobotFriendRef) Init(buf []byte, i flatbuffers.UOffsetT) {
+	rcv._tab.Bytes = buf
+	rcv._tab.Pos = i
+}
+
+func (rcv *RobotFriendRef) Table() flatbuffers.Table {
+	return rcv._tab
+}
+
+func (rcv *RobotFriendRef) Id() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(4))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func (rcv *RobotFriendRef) DisplayName() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(6))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func (rcv *RobotFriendRef) GameId() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(8))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func (rcv *RobotFriendRef) Seat() int32 {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(10))
+	if o != 0 {
+		return rcv._tab.GetInt32(o + rcv._tab.Pos)
+	}
+	return 0
+}
+
+func (rcv *RobotFriendRef) MutateSeat(n int32) bool {
+	return rcv._tab.MutateInt32Slot(10, n)
+}
+
+func RobotFriendRefStart(builder *flatbuffers.Builder) {
+	builder.StartObject(4)
+}
+func RobotFriendRefAddId(builder *flatbuffers.Builder, id flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(id), 0)
+}
+func RobotFriendRefAddDisplayName(builder *flatbuffers.Builder, displayName flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(1, flatbuffers.UOffsetT(displayName), 0)
+}
+func RobotFriendRefAddGameId(builder *flatbuffers.Builder, gameId flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(2, flatbuffers.UOffsetT(gameId), 0)
+}
+func RobotFriendRefAddSeat(builder *flatbuffers.Builder, seat int32) {
+	builder.PrependInt32Slot(3, seat, 0)
+}
+func RobotFriendRefEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
+	return builder.EndObject()
+}