chore: rewrite user-facing messages in Projects module

Conservative cleanup of frappe.throw/msgprint messages per the message style
guide; meaning, severity, and .format() arguments are unchanged:

- index bare {} placeholders as {0}/{1}/... so translators can reorder
- move f-strings / .format() / concatenation out of _() (they break gettext
  extraction and never translate)
- wrap translatable dynamic values (DocType/Select labels) in _()
- fix grammar and colloquialisms
- drop no-op _() wrapping runtime-built strings

Part of #53976.

erpnext/projects/doctype/task/task.py

@@ -144,7 +144,7 @@ class Task(NestedSet):
 				if frappe.db.get_value("Task", d.task, "status") not in ("Completed", "Cancelled"):
 					frappe.throw(
 						_(
-							"Cannot complete task {0} as its dependant task {1} are not completed / cancelled."
+							"Cannot complete task {0} as its dependent task {1} is not completed / cancelled."
 						).format(frappe.bold(self.name), frappe.bold(d.task))
 					)
 
@@ -316,7 +316,7 @@ class Task(NestedSet):
 
 	def on_trash(self):
 		if check_if_child_exists(self.name):
-			throw(_("Child Task exists for this Task. You can not delete this Task."))
+			throw(_("Child Task exists for this Task. You cannot delete this Task."))
 
 		self.update_nsm_model()
 

erpnext/projects/doctype/timesheet_detail/timesheet_detail.py

@@ -105,7 +105,7 @@ class TimesheetDetail(Document):
 	def validate_dates(self):
 		"""Validate that to_time is not before from_time."""
 		if self.from_time and self.to_time and time_diff_in_hours(self.to_time, self.from_time) < 0:
-			frappe.throw(_("To Time cannot be before from date"))
+			frappe.throw(_("To Time cannot be before From Time"))
 
 	def validate_parent_project(self, parent_project: str):
 		"""Validate that project is same as Timesheet's parent project."""