chore: apply cargo fmt + clippy cleanup across crate

Silence forward-looking dead_code on unused DAO modules, annotate
individual placeholder items, rewrite tautological assert!(true/false)
in token tests as panic! arms, and pick up fmt drift.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/ollama.rs

@@ -120,6 +120,7 @@ impl OllamaClient {
 
     /// Replace the HTTP client with one using a custom request timeout.
     /// Useful for slow models where the default 120s may be insufficient.
+    #[allow(dead_code)]
     pub fn with_request_timeout(mut self, secs: u64) -> Self {
         self.client = Client::builder()
             .connect_timeout(Duration::from_secs(5))
@@ -174,6 +175,7 @@ impl OllamaClient {
     }
 
     /// Clear the model list cache for a specific URL or all URLs
+    #[allow(dead_code)]
     pub fn clear_model_cache(url: Option<&str>) {
         let mut cache = MODEL_LIST_CACHE.lock().unwrap();
         if let Some(url) = url {
@@ -186,6 +188,7 @@ impl OllamaClient {
     }
 
     /// Clear the model capabilities cache for a specific URL or all URLs
+    #[allow(dead_code)]
     pub fn clear_capabilities_cache(url: Option<&str>) {
         let mut cache = MODEL_CAPABILITIES_CACHE.lock().unwrap();
         if let Some(url) = url {
@@ -992,7 +995,6 @@ struct OllamaEmbedResponse {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
 
     #[test]
     fn generate_photo_description_prompt_is_concise() {