Feat: support new fields for meeting mode, proposed start date and duration.

As per title

app/forms/project.py

 from flask_wtf import FlaskForm
-from wtforms import BooleanField, SelectField, StringField, TextAreaField
+from wtforms import (
+    BooleanField,
+    DateField,
+    IntegerField,
+    SelectField,
+    StringField,
+    TextAreaField,
+    validators,
+)
 from wtforms.validators import DataRequired, ValidationError
 
 
@@ -9,6 +17,18 @@ class ProjectForm(FlaskForm):
     is_student_proposal = BooleanField("Student Proposal", default=False)
     on_behalf = StringField("from", default=None)
     category = SelectField("Category", coerce=str)
+    meeting_mode = SelectField(
+        "Meeting type",
+        choices=[("", "N/A"), ("remote", "Remote"), ("in-person", "In person")],
+        coerce=str,
+        validators=[validators.Optional()],
+    )
+    proposed_start_date = DateField(
+        "Proposed start date", validators=[validators.Optional()]
+    )
+    duration_in_weeks = IntegerField(
+        "Duration (in weeks)", validators=[validators.Optional()]
+    )
 
     def validate_on_behalf(self, field):
         if self.is_student_proposal.data and not field.data:
@@ -20,3 +40,21 @@ class ProjectForm(FlaskForm):
         if field == self.category and field.data == "":
             self.category.errors += "Please choose a category for the project."
             raise ValidationError("Please choose a category for the project.")
+
+    def validate_meeting_mode(self, field):
+        if field == self.category and field.data not in ["", "remote", "in-person"]:
+            self.meeting_mode.errors += "Invalid meeting mode."
+            raise ValidationError(
+                "The meeting mode for the project is invalid. Choose a valid value or leave it blank."
+            )
+
+    def validate_duration(self, field):
+        if (
+            field == self.duration_in_weeks
+            and field.data is not None
+            and field.data < 0
+        ):
+            self.meeting_mode.errors += "Invalid duration."
+            raise ValidationError(
+                "The duration for the project is invalid. Choose a valid value or leave it blank."
+            )