feat(ai): iteration budget in prompt + preserve photo-knowledge links

- Inject the max-iterations budget into the agentic system prompt for
  both insight generation and chat turns. Chat does this per-turn by
  appending a note to the replayed system message and restoring it
  before persistence so the note doesn't accumulate across turns.
- Stop deleting entity_photo_links at the start of agentic insight
  generation. The clear made recall_facts_for_photo always return
  empty, wasting a tool call and discarding knowledge from prior runs.
  Re-linking the same entity is already an INSERT OR IGNORE no-op.

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

src/ai/insight_generator.rs

@@ -2892,8 +2892,11 @@ Return ONLY the summary, nothing else."#,
                 .collect()
         };
 
-        // 6. Clear existing entity-photo links for this file so the run starts fresh,
-        //    and ensure the owner entity exists so the agent can reference it.
+        // 6. Ensure the owner entity exists so the agent can reference it.
+        //    Prior entity_photo_links for this file are intentionally preserved
+        //    across regenerations — clearing them made `recall_facts_for_photo`
+        //    always return empty and discarded hard-won knowledge. Re-linking
+        //    the same entity is a no-op (INSERT OR IGNORE).
         let owner_name = user_display_name();
         let owner_entity_id: Option<i32> = {
             let mut kdao = self
@@ -2901,14 +2904,6 @@ Return ONLY the summary, nothing else."#,
                 .lock()
                 .expect("Unable to lock KnowledgeDao");
 
-            if let Err(e) = kdao.delete_photo_links_for_file(&insight_cx, &file_path) {
-                log::warn!(
-                    "Failed to clear entity_photo_links for {}: {:?}",
-                    file_path,
-                    e
-                );
-            }
-
             // Upsert the owner entity so the agent always has a stable entity ID to reference.
             let owner = crate::database::models::InsertEntity {
                 name: owner_name.clone(),
@@ -3000,9 +2995,11 @@ Return ONLY the summary, nothing else."#,
             4. Use recall_entities to look up known people, places, or things that appear in this photo.\n\
             5. When you identify people, places, events, or notable things in this photo: use store_entity to record them and store_fact to record key facts (relationships, roles, attributes). This builds a persistent memory for future insights.\n\
             6. Only produce your final insight AFTER you have gathered context from at least 5 tool calls.\n\
-            7. If a tool returns no results, that is useful information — continue calling the remaining tools anyway.",
+            7. If a tool returns no results, that is useful information — continue calling the remaining tools anyway.\n\
+            8. You have a hard budget of {max_iterations} tool-calling iterations before the loop ends. Plan your context gathering so you can write a complete final insight within that budget.",
             owner_id_note = owner_id_note,
-            owner_name = owner_name
+            owner_name = owner_name,
+            max_iterations = max_iterations
         );
         let system_content = if let Some(ref custom) = custom_system_prompt {
             format!("{}\n\n{}", custom, base_system)