Refactor containers to template literals for independent updates

- Extract all containers (login, notes list, note detail, note form, conversation form, conversations list) to CONTAINERS object
- Create initializeContainers() function to inject templates on page load
- Replace 300+ lines of inline HTML with single containerHost div
- Add session log documenting Option 1 approach with future intent for Option 2
- Each container now independently updatable without touching markup
- Maintains functionality while improving code organization and maintainability

logs/SESSION_LOG.txt

@@ -0,0 +1,19 @@
+================================================================================
+PRISM NOTES - SESSION LOG
+Project history, decisions, and architectural milestones
+================================================================================
+
+[2026-01-10 14:00] Container Refactoring: Template Literals (Option 1)
+- Decision: Extracted all container HTML to template literals in index.html
+- Reasoning: Allows independent container updates without touching markup
+  Each container is now self-contained and versioned separately
+- Implementation: 
+  * Created CONTAINERS object with keys: login, notesList, noteDetail, noteForm, 
+    conversationForm, conversationsList
+  * Added initializeContainers() function that injects all templates on page load
+  * Containers maintained in-file for simplicity during active development
+- Future Intent: Migrate to Option 2 (separate files in containers/) when project 
+  becomes more established and needs full file separation
+- Status: Functional and ready for independent container updates
+
+================================================================================