feat: add project code generation + remove issues/milestones from nav

app/models/models.py

@@ -92,6 +92,7 @@ class Project(Base):
 
     id = Column(Integer, primary_key=True, index=True)
     name = Column(String(100), unique=True, nullable=False)
+    project_code = Column(String(16), unique=True, index=True, nullable=True)
     description = Column(Text, nullable=True)
     created_at = Column(DateTime(timezone=True), server_default=func.now())
     
@@ -131,3 +132,11 @@ class ProjectMember(Base):
     
     project = relationship("Project", back_populates="members")
     user = relationship("User", back_populates="project_memberships")
+
+
+class ProjectCodeCounter(Base):
+    __tablename__ = project_code_counters
+
+    id = Column(Integer, primary_key=True, index=True)
+    prefix = Column(String(16), unique=True, index=True, nullable=False)
+    next_value = Column(Integer, default=0)