Harden public intake bounds against untrusted growth (#1451)

* Bound public rate-limit buckets against attacker-keyed growth.

Keep the NIP-13 PoW sender bypass, skip content-bucket minting on
sender reject, and evict idle/oldest entries at a hard cap.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Stop Cashu-looking text from skipping long-message guards.

Oversized public content always collapses and takes the plain
formatting path so remote tokens cannot force layout/regex DoS.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Cap teleported geohash participant markers.

Bound the set with FIFO eviction, clear it on channel switch, and
prune markers that leave the visible participant list.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Bound untrusted Nostr relay frames and event tags.

Reject oversized inbound messages before JSON parse, cap tag
arrays/values at decode, and stop logging raw tag contents.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Fail soft when Noise handshake state is unexpectedly missing.

Replace the initiator startHandshake force unwrap with a guard
that throws invalidState instead of crashing.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Cap geohash nickname cache from remote Nostr events.

FIFO-evict at capacity, clear on channel switch, and prune
nicknames that leave the visible participant list.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Avoid overlapping exclusive access in the rate limiter.

Make bucket helpers static so inout dictionary updates do not
conflict with a mutating call on self.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Fix rate-limiter tests for mutating allow under #expect.

Call allow outside the macro so Swift Testing does not capture an
immutable copy of the struct.

Co-authored-by: Cursor <cursoragent@cursor.com>

* Drop unused WebSocket data helper; reset rate limiter on panic wipe.

dataWithinInboundLimit replaced the unbounded path, and panic clear
should not leave public intake buckets behind.

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

bitchatTests/AppArchitectureTests.swift

@@ -147,6 +147,44 @@ struct AppArchitectureTests {
         #expect(store.teleportedGeo.isEmpty)
     }
 
+    @Test("LocationPresenceStore bounds and prunes teleported geohash participants")
+    @MainActor
+    func locationPresenceStoreBoundsTeleportedParticipants() {
+        let store = LocationPresenceStore(teleportedGeoCapacity: 2)
+
+        store.setCurrentGeohash("u4pruy")
+        store.markTeleported("AAAAAA")
+        store.markTeleported("BBBBBB")
+        store.markTeleported("CCCCCC")
+
+        #expect(store.teleportedGeo == Set(["bbbbbb", "cccccc"]))
+
+        store.retainTeleportedGeo(keeping: Set(["CCCCCC"]))
+        #expect(store.teleportedGeo == Set(["cccccc"]))
+
+        store.setCurrentGeohash("u4pruz")
+        #expect(store.teleportedGeo.isEmpty)
+    }
+
+    @Test("LocationPresenceStore bounds geohash nicknames and clears on channel switch")
+    @MainActor
+    func locationPresenceStoreBoundsGeoNicknames() {
+        let store = LocationPresenceStore(geoNicknameCapacity: 2)
+
+        store.setCurrentGeohash("u4pruy")
+        store.setNickname("alice", for: "AAAAAA")
+        store.setNickname("bob", for: "BBBBBB")
+        store.setNickname("carol", for: "CCCCCC")
+
+        #expect(store.geoNicknames == ["bbbbbb": "bob", "cccccc": "carol"])
+
+        store.retainGeoNicknames(keeping: Set(["CCCCCC"]))
+        #expect(store.geoNicknames == ["cccccc": "carol"])
+
+        store.setCurrentGeohash("u4pruz")
+        #expect(store.geoNicknames.isEmpty)
+    }
+
     @Test("PeerHandle equality and hashing use the canonical identity only")
     func peerHandleEqualityUsesCanonicalIdentity() {
         let first = PeerHandle(id: "noise:abc123", routingPeerID: PeerID(str: "peer-a"))