feat: Complete backend and docs rebrand from Patherly to ResolutionFlow

Update APP_NAME, OpenAPI metadata, log messages, root endpoint response,
model docstrings, seed script comments, README heading, and CLAUDE.md
branding references. Frontend rebrand was completed in PR #26; this
covers everything else.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/models/category.py

@@ -16,7 +16,7 @@ class TreeCategory(Base):
     """Admin-managed categories for organizing trees.
 
     Categories can be:
-    - Global (team_id=NULL): Created by Patherly admins, visible to all
+    - Global (team_id=NULL): Created by ResolutionFlow admins, visible to all
     - Team-specific (team_id set): Created by team admins, visible to team members
     """
     __tablename__ = "tree_categories"

backend/app/models/step_category.py

@@ -15,7 +15,7 @@ class StepCategory(Base):
     """Admin-managed categories for organizing step library entries.
 
     Categories can be:
-    - Global (team_id=NULL): Created by Patherly admins, visible to all
+    - Global (team_id=NULL): Created by ResolutionFlow admins, visible to all
     - Team-specific (team_id set): Created by team admins, visible to team members
     """
     __tablename__ = "step_categories"

backend/app/models/user.py

@@ -50,7 +50,7 @@ class User(Base):
 
     @property
     def is_admin(self) -> bool:
-        """Returns True if user is a global (Patherly) admin."""
+        """Returns True if user is a global (ResolutionFlow) admin."""
         return self.role == "admin"
 
     @property