Pair transfers from rules.toml

The boolean transfer flag went two commits ago because a one-sided verdict let
half a movement vanish and left the report unbalanced. This is what replaces
it: a [[transfer]] block names both legs, and only a matched pair is dropped
from the report -- both legs together, never one.

Legs pair within five days, nearest date first, and a transaction belongs to at
most one transfer, so the first definition to claim a leg keeps it, exactly as
the first matching rule keeps a tag. The pairing is derived state like the tags:
Engine.Link rewrites the whole transfers table from rules.toml, which is why
retag re-derives both halves of what that file decides, and why it runs over
the whole index rather than a filtered view -- pairing inside one would let a
movement count as a transfer in one report and not in another. An unmatched leg
is not a transfer and keeps counting, surfaced as a warning instead.

Within one currency the amount is the evidence and must be the exact opposite.
Across currencies it is not checked at all: there are no rates here, so the two
numbers are unrelated and the dates carry the pairing alone.

tolerance_pct is the one exception, per definition, for a route where the bank
takes a fee and the two statements genuinely disagree. It defaults to zero and
belongs on the one definition that charges; a global or default tolerance would
loosen every route that does not. The difference it admits is not forgiven --
the pair leaves the report entirely, so a fee hidden inside one would be
spending that appears nowhere. Pair.Fee is what left less what arrived, and
report.Excluded carries it out per currency alongside the legs. It counts only
pairs whose legs are both in view, for the same reason it counts legs and not
transfers: half a pair cannot say what the other half received.

The screens:

- 6 builds a definition against the index as you type, showing the pairs it
  would form and the legs it would catch but leave unpaired. Six fields need
  more room than the rule builder's four, so the form sheds its spacing, then
  its hints, then the borders on unfocused fields.
- 7 lists every definition with what it pairs. Two counts, because they mean
  different things: an unpaired leg is a definition doing something and not
  finishing it, no pairs at all is dead weight. Tol names the tolerance, blank
  where amounts must agree.
- 3 grows a (transfers) row under TOTAL, and a fees row beneath it, or the
  report silently disagrees with the account balances.

Two things that are not part of transfers but are the same day's work:

- ls --uniq lists each account and description once, normalised the way a glob
  sees them, which is the shape of "what still needs a rule?" -- fifty visits
  to one shop are one pattern to write, not fifty rows to read.
- The rule builder's preview now filters to what the glob matches instead of
  marking matches in a full list. The count carries the context the rows no
  longer can: 2 of 7, measured against everything still in view.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/importer/importer.go

@@ -19,6 +19,7 @@ import (
 	"git.petrovv.com/nikola/money/internal/parser"
 	"git.petrovv.com/nikola/money/internal/rules"
 	"git.petrovv.com/nikola/money/internal/store"
+	"git.petrovv.com/nikola/money/internal/transfers"
 )
 
 // FileResult is what happened to one statement file.
@@ -38,6 +39,11 @@ type FileResult struct {
 type Result struct {
 	Files    []FileResult
 	Retagged int
+	// Paired and Unpaired are the state of the transfer pairing after the
+	// import: how many movements were matched, and how many legs a definition
+	// caught without finding the other side.
+	Paired   int
+	Unpaired int
 }
 
 // Total counts new rows across every file.
@@ -69,8 +75,12 @@ type Options struct {
 	Force bool
 }
 
-// Run imports every account under root into db and then applies the rules.
-func Run(root string, db *store.DB, accounts []*config.Account, engine *rules.Engine, opts Options) (Result, error) {
+// Run imports every account under root into db and then applies the rules and
+// the transfer definitions. Both are derived from rules.toml and both are
+// recomputed over the whole index, since a statement imported now can complete
+// a transfer whose other leg arrived months ago.
+func Run(root string, db *store.DB, accounts []*config.Account, engine *rules.Engine,
+	links *transfers.Engine, opts Options) (Result, error) {
 	var res Result
 	for _, acc := range accounts {
 		accountID, err := db.UpsertAccount(model.Account{
@@ -106,6 +116,12 @@ func Run(root string, db *store.DB, accounts []*config.Account, engine *rules.En
 		return res, err
 	}
 	res.Retagged = n
+
+	paired, unpaired, err := links.Link(db)
+	if err != nil {
+		return res, err
+	}
+	res.Paired, res.Unpaired = paired, unpaired
 	return res, nil
 }