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

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

src/models/user.rs

@@ -24,6 +24,29 @@ pub struct AuthInfo {
     pub avatar_url: String,
 }
 
+/// Per-user LLM provider configuration stored in MongoDB.
+///
+/// Controls which provider and model the user's chat sessions default
+/// to, and stores API keys for non-Ollama providers.
+#[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]
+pub struct UserProviderConfig {
+    /// Default provider name (e.g. "ollama", "openai")
+    pub default_provider: String,
+    /// Default model ID (e.g. "llama3.1:8b", "gpt-4o")
+    pub default_model: String,
+    /// OpenAI API key (empty if not configured)
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub openai_api_key: Option<String>,
+    /// Anthropic API key
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub anthropic_api_key: Option<String>,
+    /// HuggingFace API key
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub huggingface_api_key: Option<String>,
+    /// Custom Ollama URL override (empty = use server default)
+    pub ollama_url_override: String,
+}
+
 /// Per-user preferences stored in MongoDB.
 ///
 /// Keyed by `sub` (Keycloak subject) and optionally scoped to an org.
@@ -41,4 +64,7 @@ pub struct UserPreferences {
     pub ollama_model_override: String,
     /// Recently searched queries for quick access
     pub recent_searches: Vec<String>,
+    /// LLM provider configuration
+    #[serde(default)]
+    pub provider_config: UserProviderConfig,
 }