Bundle a static pdftotext into the binary

The PDF parsers shell out to pdftotext, so every machine running money needed
poppler-utils installed. scripts/build-bundled.sh now builds a deployable
binary that carries its own: pdftotext is compiled in a container from a
checksum-pinned poppler release as a fully static musl executable, then
embedded with `go build -tags bundled`. The result is one file that runs on
any Linux of that architecture with nothing installed alongside it.

It is still the real pdftotext, run as a subprocess. Linking poppler through
cgo would have cost the pure-Go build, and its C++ text API is not guaranteed
to space columns the way pdftotext -layout does, which is what the parsers
were tuned on. Only what text extraction needs is compiled in -- no
fontconfig, cairo or image codecs -- and its output is byte-identical to a
full distro build on the same PDF.

At runtime the embedded copy is written to the user cache directory, not
/tmp, which servers often mount noexec. It is named by content hash, so a
newer build never runs an older copy, and verified before reuse, so a write cut
short by a killed process is replaced rather than trusted. `money config` says
which pdftotext is in use.

The tag is opt-in: plain go build and go test never need the 5 MB executable,
which is gitignored rather than committed. Building with the tag for anything
but linux/amd64 or linux/arm64 fails with a message saying so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/parser/bundled_linux_amd64.go

@@ -0,0 +1,13 @@
+//go:build bundled
+
+package parser
+
+import _ "embed"
+
+// Built by scripts/build-bundled.sh amd64, which also runs the go build that
+// needs it. The file is not checked in, so this only compiles after that.
+//
+//go:embed bundled/pdftotext-linux-amd64
+var embeddedPdftotext []byte
+
+func init() { bundledPdftotext = embeddedPdftotext }