feat(chat): added chat interface and connection to ollama (#10)

Co-authored-by: Sharang Parnerkar <parnerkarsharang@gmail.com>
Reviewed-on: #10

src/infrastructure/database.rs

@@ -3,7 +3,7 @@
 use mongodb::{bson::doc, Client, Collection};
 
 use super::Error;
-use crate::models::{OrgBillingRecord, OrgSettings, UserPreferences};
+use crate::models::{ChatMessage, ChatSession, OrgBillingRecord, OrgSettings, UserPreferences};
 
 /// Thin wrapper around [`mongodb::Database`] that provides typed
 /// collection accessors for the application's domain models.
@@ -49,4 +49,20 @@ impl Database {
     pub fn org_billing(&self) -> Collection<OrgBillingRecord> {
         self.inner.collection("org_billing")
     }
+
+    /// Collection for persisted chat sessions (sidebar listing).
+    pub fn chat_sessions(&self) -> Collection<ChatSession> {
+        self.inner.collection("chat_sessions")
+    }
+
+    /// Collection for individual chat messages within sessions.
+    pub fn chat_messages(&self) -> Collection<ChatMessage> {
+        self.inner.collection("chat_messages")
+    }
+
+    /// Raw BSON document collection for queries that need manual
+    /// `_id` → `String` conversion (avoids `ObjectId` deserialization issues).
+    pub fn raw_collection(&self, name: &str) -> Collection<mongodb::bson::Document> {
+        self.inner.collection(name)
+    }
 }