Add adjustable context size, custom chatbot name, and cat icon for AI chat

Settings > AI tab now includes context size slider (2048–131072) with VRAM
estimate and a chatbot name field. ChatService reads both dynamically instead
of hardcoding num_ctx=16384 and "Purrse AI". Chat panel FAB and empty state
use mdi-cat icon to match the rest of the app.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/views/settings/SettingsView.vue

@@ -762,6 +762,37 @@
           </v-card-text>
         </v-card>
 
+        <v-card class="mt-4">
+          <v-card-title>AI Chat Settings</v-card-title>
+          <v-card-text>
+            <div class="text-body-2 mb-1">Context Size: {{ aiSettings.chatContextSize.toLocaleString() }} tokens</div>
+            <v-slider
+              v-model="aiSettings.chatContextSize"
+              :min="2048"
+              :max="131072"
+              :step="2048"
+              thumb-label
+              color="primary"
+              hide-details
+              class="mb-1"
+            />
+            <div class="text-caption text-medium-emphasis mb-4">
+              Estimated VRAM: ~{{ Math.round((aiSettings.chatContextSize / 1024) * 75) }} MB — Increase if the AI loses context in long chats. Decrease if Ollama runs out of memory.
+            </div>
+
+            <v-text-field
+              v-model="aiSettings.chatBotName"
+              label="Chatbot Name"
+              variant="outlined"
+              density="compact"
+              placeholder="Purrse AI"
+              hint="Custom name shown in the chat panel header and used by the AI"
+              persistent-hint
+              clearable
+            />
+          </v-card-text>
+        </v-card>
+
         <v-snackbar v-model="showAiSuccess" :timeout="4000" color="success">
           AI categorization settings saved
         </v-snackbar>
@@ -1305,7 +1336,9 @@ const aiSettings = reactive<AiCategorizationSettings>({
   timeoutSeconds: 30,
   updatePayeeDefaults: true,
   systemPrompt: null,
-  userPromptTemplate: null
+  userPromptTemplate: null,
+  chatContextSize: 16384,
+  chatBotName: null
 })
 const aiSaving = ref(false)
 const aiTesting = ref(false)