fix: add values_callable to all SQLAlchemy Enum columns

SQLAlchemy 2.0 defaults to mapping Python enum *names* (OPEN, CLOSED)
to DB values, but MySQL stores lowercase *values* (open, closed).
This mismatch causes LookupError on read.

Adding values_callable=lambda x: [e.value for e in x] tells SQLAlchemy
to use the enum values for DB mapping.

Affected models: milestone, task, meeting, propose, support

app/models/task.py

@@ -23,8 +23,8 @@ class Task(Base):
     id = Column(Integer, primary_key=True, index=True)
     title = Column(String(255), nullable=False)
     description = Column(Text, nullable=True)
-    status = Column(Enum(TaskStatus), default=TaskStatus.OPEN)
-    priority = Column(Enum(TaskPriority), default=TaskPriority.MEDIUM)
+    status = Column(Enum(TaskStatus, values_callable=lambda x: [e.value for e in x]), default=TaskStatus.OPEN)
+    priority = Column(Enum(TaskPriority, values_callable=lambda x: [e.value for e in x]), default=TaskPriority.MEDIUM)
     task_code = Column(String(64), nullable=True, unique=True, index=True)
     
     # Task type/subtype (replaces old issue_type/issue_subtype)