feat: visualization of conversation affinity in dashboard

doc/monitoring.md

@@ -166,6 +166,39 @@ curl -X POST http://localhost:12434/api/cache/invalidate
 
 Clears all cached entries and resets hit/miss counters.
 
+### Affinity Stats (Conversation Affinity)
+
+```bash
+curl http://localhost:12434/api/affinity_stats
+```
+
+Response when [`conversation_affinity`](configuration.md#conversation_affinity) is enabled:
+
+```json
+{
+  "enabled": true,
+  "ttl": 300,
+  "entries": [
+    { "endpoint": "http://gpu-primary:11434",   "model": "llama3.2:latest",     "remaining": 287.4 },
+    { "endpoint": "http://gpu-primary:11434",   "model": "llama3.2:latest",     "remaining": 113.0 },
+    { "endpoint": "http://gpu-secondary:11434", "model": "qwen2.5-coder:7b",    "remaining":  44.8 }
+  ]
+}
+```
+
+Response when the feature is disabled:
+```json
+{ "enabled": false, "ttl": 300, "entries": [] }
+```
+
+- One element per **live pinned conversation** (no fingerprints or content — just the endpoint/model the pin points to and how many seconds it has left before expiry).
+- Aggregation by `(endpoint, model)` is left to the consumer: the dashboard does this client-side.
+- The endpoint is gated by the same `nomyo-router-api-key` middleware as the rest of `/api/*`.
+
+The dashboard's **Running Models (PS) → Affinity** column is rendered from this data. The column auto-hides when `enabled: false`. Each row shows one dot per live pin against that `(endpoint, model)` pair; dot opacity = `remaining / ttl` (floor 0.15), so freshly-routed pins are solid and pins close to expiry fade out. A `+N` overflow badge appears once a single (endpoint, model) holds more than 12 active pins; an em-dash (`—`) marks an `(endpoint, model)` with no live pins.
+
+> Multiple dots for what looks like "one chat window" is normal — most chat UIs (Open WebUI, LibreChat, …) fire auxiliary requests (title generation, follow-up suggestions, tag extraction) that have their own first-turn fingerprint and therefore their own pin. See [Conversation Affinity → Why the dashboard may show more than one dot per visible conversation](configuration.md#conversation_affinity) for the details.
+
 ### Real-time Usage Stream
 
 ```bash