Capture tasks, with one intake seam mail can call later (#130)

A task is not a fact and not a note. A fact is a claim about the world that a
correction supersedes; a note is something to recall by meaning. A task is work
with a lifecycle, and the read that matters is "everything outstanding right
now" — which over an append-only log would mean replaying history on every
question. So: a tasks table, migration #14, statuses candidate/open/done/dropped
that each move forward exactly once.

Dedupe is on normalised text among LIVE rows only, via a partial unique index.
That is the property the mail side needs: an extractor may call CaptureTask for
every message it reads, as often as it likes, without growing the list — while a
weekly errand is still capturable again once the last one is done.

Three ways in, one seam. ipc.CaptureTaskReq is it: the voice path
(router.ParseTaskCapture on an explicit marker — "добавь в задачи …", never
"надо бы поспать"), the /tasks form, and the email reader from #246 when it
exists. Mail-derived items set Source "email:<account>", Status "candidate" and
Evidence to whatever makes the row reviewable; a candidate is inert until he
confirms it on /tasks, and Maven names it as unconfirmed when she recites the
list rather than putting words in his mouth.

No new intent — the router enum is a contract with the relabelling prompt, so
capture rides the note intent and the list rides a query source, both matched
deterministically like the calendar and plan matchers already are.

Nothing here speaks. No tick rule reads tasks; the list is answered when asked
about, which is why /tasks POST is not step-up gated the way /tools and
/routines are — a task write moves no boundary.

Vikunja #130

internal/auth/policy.go

@@ -65,7 +65,16 @@ func Requirement(m ipc.Method) Authority {
 		ipc.MethodCreateReminder,
 		ipc.MethodMarkReminder,
 		ipc.MethodRecordNudge,
-		ipc.MethodResolveNudge:
+		ipc.MethodResolveNudge,
+		// Task capture (Vikunja #130). Listed explicitly rather than left to
+		// the default so the intent is on the record: capturing a task is a
+		// module write, not an allowlist mutation and not a new standing reason
+		// for Maven to speak — nothing in the tick loop reads tasks. It stays
+		// at AuthRead, the same rung as CreateReminder, which is the closest
+		// existing analogue.
+		ipc.MethodCaptureTask,
+		ipc.MethodListTasks,
+		ipc.MethodSetTaskStatus:
 		return AuthRead
 	}
 	// Unknown method ⇒ AuthRead, but ipc.dispatch returns ErrUnknownMethod