refactor: Replace all 'PUI' references with 'moneyflow' for consistency

Updated all remaining 'Finance PUI' and 'PUI' references to 'moneyflow'
for complete branding consistency.

**Changes:**
- App title: "Finance PUI" → "moneyflow"
- Demo mode title: "Finance PUI [DEMO MODE]" → "moneyflow [DEMO MODE]"
- backends/__init__.py: "the PUI" → "moneyflow"
- backends/base.py: "the PUI" → "moneyflow" (2 instances)
- backends/monarch.py: "the PUI" → "moneyflow"

**Branding Now 100% Consistent:**
- App window title shows "moneyflow"
- All code comments reference "moneyflow"
- No remnants of old "PUI" name
- Demo mode clearly marked

**PUI History:**
PUI was an early project name ("Power User Interface" or "Personal UI")
that has been superseded by the final product name "moneyflow".

All 465 tests passing, pyright clean.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: wesm

moneyflow/app.py

@@ -161,9 +161,9 @@ def __init__(
         self.mm = None
         if demo_mode:
             self.mm = DemoBackend(year=start_year or 2025)
-            self.title = "Finance PUI [DEMO MODE]"
+            self.title = "moneyflow [DEMO MODE]"
         else:
-            self.title = "Finance PUI"
+            self.title = "moneyflow"
         self.data_manager: Optional[DataManager] = None
         self.state = AppState()
         self.loading = False

moneyflow/backends/__init__.py

@@ -1,7 +1,7 @@
 """
 Finance backend abstraction layer.
 
-This module provides a pluggable backend system that allows the PUI to work
+This module provides a pluggable backend system that allows moneyflow to work
 with different finance platforms (Monarch Money, YNAB, etc.) through a
 common interface.
 

moneyflow/backends/base.py

@@ -2,7 +2,7 @@
 Abstract base class for finance backend implementations.
 
 This defines the interface that all finance backends (Monarch, YNAB, etc.) must implement
-to be compatible with the PUI.
+to be compatible with moneyflow.
 """
 
 from abc import ABC, abstractmethod
@@ -13,7 +13,7 @@ class FinanceBackend(ABC):
     """
     Abstract base class for finance backend implementations.
 
-    All backends must implement these methods to be compatible with the PUI.
+    All backends must implement these methods to be compatible with moneyflow.
     This allows the UI layer to work with any supported finance platform.
     """
 

moneyflow/backends/monarch.py

@@ -14,7 +14,7 @@ class MonarchBackend(FinanceBackend):
     Monarch Money backend implementation.
 
     This wraps the MonarchMoney GraphQL client to provide a standardized
-    FinanceBackend interface for the PUI.
+    FinanceBackend interface for moneyflow.
     """
 
     def __init__(self):