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/store/migrations.go

@@ -131,6 +131,35 @@ ALTER TABLE reminders ADD COLUMN next_fire_ts INTEGER;`, // #2
 		expires_ts INTEGER NOT NULL
 	);
 	CREATE INDEX IF NOT EXISTS idx_digest_entries_status ON digest_entries (status);`,
+
+	// #14 — the task capture store (Vikunja #130). Deliberately NOT facts:
+	// a fact is a claim about the world that gets superseded, a task is a
+	// piece of work with a lifecycle (captured → open → done), and the
+	// prioritiser needs to read the live set cheaply.
+	//
+	// status: 'candidate' is a task Maven derived from something she read
+	// (mail, later) and has NOT been confirmed by the owner; 'open' is a task
+	// he actually stated (or confirmed). Nothing schedules or announces off
+	// this table — capture is not a nag.
+	//
+	// norm is the normalised dedupe key. The unique index is PARTIAL, over
+	// live rows only: re-capturing "купить молоко" after last week's one is
+	// done must work, while the same mail arriving twice must not produce two
+	// rows.
+	`CREATE TABLE IF NOT EXISTS tasks (
+		id          INTEGER PRIMARY KEY AUTOINCREMENT,
+		created_ts  INTEGER NOT NULL,
+		text        TEXT    NOT NULL,
+		norm        TEXT    NOT NULL,
+		source      TEXT    NOT NULL,
+		evidence    TEXT    NOT NULL DEFAULT '',
+		status      TEXT    NOT NULL DEFAULT 'open' CHECK (status IN ('candidate','open','done','dropped')),
+		due_ts      INTEGER,
+		weight      INTEGER NOT NULL DEFAULT 0,
+		resolved_ts INTEGER
+	);
+	CREATE UNIQUE INDEX IF NOT EXISTS idx_tasks_live_norm ON tasks (norm) WHERE status IN ('candidate','open');
+	CREATE INDEX IF NOT EXISTS idx_tasks_status ON tasks (status, created_ts DESC);`,
 }
 
 // migrate applies every migration with a number greater than the DB's current