fix(dm): ownership transfer divergence after back-and-forth — canonicalize ownerHomeInstance + normalize authority checks

Manual ownership transfers between two federated instances diverged because
`dm_channels.ownerHomeInstance` was stored as a BARE host (`orbit.ddns.net`)
for federated owners — via `transferGroupDmOwnership` copying `users.homeInstance`
verbatim — while `sourceInstance` always arrives as a full URL on the wire.
`processOwnershipTransferEvent` and `processMemberRemoveEvent` then compared the
two with strict equality and rejected legitimate inbound events as
`unauthorized_source`, keeping ownership permanently divergent across peers.
Live DB inspection on the two test instances confirmed both rows (nova + orbit)
had a BARE `owner_home_instance`, matching the bug report exactly.

Three compounding fixes:

1. Receiver authority checks now compare via `normalizeOriginForCompare` so
   legacy bare-vs-full rows accept legitimate transfers (and kicks).
2. New `canonicalizeHomeInstance` helper in `federationAuth.ts`; every write
   site that persists `ownerHomeInstance` (`transferGroupDmOwnership`, group DM
   creation, lazy federation in member-add, `processMemberAddEvent` bootstrap,
   `processOwnershipTransferEvent` receiver storage) routes through it. Full URL
   is the canonical storage form, matching how `sourceInstance` arrives.
3. `dm_owner_updated` WS event extended with optional `newOwnerHomeUserId` and
   `newOwnerHomeInstance` fields. Client `updateDmOwner` writes them when
   present and leaves existing values untouched otherwise (legacy-server safe).
   Without this, `getOwnerInstanceForDm` returned the previous owner's home
   after a successful WS broadcast, routing the next owner-only op to the wrong
   instance.

Coverage: new `federation.ownershipTransfer.test.ts` (7 receiver tests including
the headline bare-vs-full regression and the dedup replay guard); new bare-vs-full
case in `federation.kick.test.ts`; two new client-side cases in
`groupDm.ownerRouting.test.ts` covering both the extended-payload write path and
the legacy-server passthrough. Tests: 1053 server + 364 web, all green.

Specs updated: `dm-system.md` historical bugs + frontend handler table + WS
state-change events table; `federation.md` `ownership_transfer` receiver flow;
`websocket.md` event-fields table.

packages/web/src/stores/spaceStore.ts

@@ -129,7 +129,12 @@ interface SpaceState {
   removeDmChannel: (id: string) => void;
   addDmMember: (dmChannelId: string, user: User) => void;
   removeDmMember: (dmChannelId: string, userId: string) => void;
-  updateDmOwner: (dmChannelId: string, newOwnerId: string) => void;
+  updateDmOwner: (
+    dmChannelId: string,
+    newOwnerId: string,
+    newOwnerHomeUserId?: string,
+    newOwnerHomeInstance?: string,
+  ) => void;
   updateDmMetadata: (dmChannelId: string, patch: { name?: string | null; icon?: string | null }) => void;
   closeDm: (id: string) => Promise<void>;
   leaveDm: (id: string) => Promise<void>;
@@ -321,10 +326,19 @@ export const useSpaceStore = create<SpaceState>((set, get) => ({
     ),
   })),
 
-  updateDmOwner: (dmChannelId, newOwnerId) => set((state) => ({
-    dmChannels: state.dmChannels.map(dm =>
-      dm.id === dmChannelId ? { ...dm, ownerId: newOwnerId } : dm
-    ),
+  updateDmOwner: (dmChannelId, newOwnerId, newOwnerHomeUserId, newOwnerHomeInstance) => set((state) => ({
+    dmChannels: state.dmChannels.map(dm => {
+      if (dm.id !== dmChannelId) return dm;
+      const next = { ...dm, ownerId: newOwnerId };
+      // Only overwrite the federation routing fields when the caller supplies
+      // them. Older servers that omit these fields must not blank out the
+      // existing values — the DM would otherwise lose its owner-routing data
+      // and `getOwnerInstanceForDm` would silently fall back to '' (home),
+      // re-introducing the bug this WS extension fixes.
+      if (newOwnerHomeUserId !== undefined) next.ownerHomeUserId = newOwnerHomeUserId;
+      if (newOwnerHomeInstance !== undefined) next.ownerHomeInstance = newOwnerHomeInstance;
+      return next;
+    }),
   })),
 
   // Patches the group DM's display metadata (name + icon). Idempotent: a