Stage 17 round 6 (#16/#17, PR C): lobby sort + server-derived in-game friend state

Lobby: group the my-games list into your-turn / opponent-turn / finished
(empty sections hidden), ordered by last activity (your-turn oldest-first,
the other two newest-first), as a compact line-separated list. gameDTO and
FB GameView gain last_activity_unix (turn start while active, finish time
once finished); a pure lib/lobbysort.ts holds the grouping/ordering.

Friends: the in-game 'add to friends' item is now server-derived via a new
GET /user/friends/outgoing (+ friends.outgoing op), returning addressees with
a pending OR declined request (both read as 'request sent'), so it is correct
across reloads; it shows a disabled '✓ in friends' once accepted. It
live-updates when the opponent answers: RespondFriendRequest now publishes
friend_added (accept) / friend_declined (new notify sub-kind, decline) to the
original requester, whose open game re-derives its friend state.

Tests: lobbysort unit test; gateway outgoing + last_activity transcode tests;
backend integration ListOutgoingRequests + respond-publishes-to-requester;
e2e updated for the new lobby section labels + a non-friend active opponent.
Docs: ARCHITECTURE notify catalog, FUNCTIONAL(+ru) lobby/friends, PLAN.

ui/src/lib/codec.ts

@@ -249,6 +249,7 @@ function decodeGameView(g: fb.GameView): GameView {
     turnTimeoutSecs: g.turnTimeoutSecs(),
     moveCount: g.moveCount(),
     endReason: s(g.endReason()),
+    lastActivityUnix: Number(g.lastActivityUnix()),
     seats,
   };
 }
@@ -587,6 +588,16 @@ export function decodeIncomingList(buf: Uint8Array): AccountRef[] {
   return out;
 }
 
+export function decodeOutgoingList(buf: Uint8Array): AccountRef[] {
+  const l = fb.OutgoingRequestList.getRootAsOutgoingRequestList(new ByteBuffer(buf));
+  const out: AccountRef[] = [];
+  for (let i = 0; i < l.requestsLength(); i++) {
+    const r = l.requests(i);
+    if (r) out.push(decodeAccountRef(r));
+  }
+  return out;
+}
+
 export function decodeBlockList(buf: Uint8Array): AccountRef[] {
   const l = fb.BlockList.getRootAsBlockList(new ByteBuffer(buf));
   const out: AccountRef[] = [];
@@ -678,6 +689,7 @@ function emptyGame(): GameView {
     turnTimeoutSecs: 0,
     moveCount: 0,
     endReason: '',
+    lastActivityUnix: 0,
     seats: [],
   };
 }