Fork Notesium source and restructure into Go package layout

Initial fork of github.com/alonswartz/notesium into librenotes:
- Source moved to internal/notesium/ (package notesium)
- Thin entry point at cmd/librenotes/main.go
- Module renamed to git.librete.ch/public/librenotes
- main() exposed as notesium.Run()
- LICENSE preserved (MIT), NOTICE added with attribution
- Web assets and completion.bash co-located with embedding code
  to satisfy go:embed path constraints

Closes #3, #34, #35.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/notesium/web/graph/make.sh

@@ -0,0 +1,60 @@
+#!/bin/bash -e
+
+fatal() { echo "Fatal: $*" 1>&2; exit 1; }
+
+usage() {
+cat<<EOF
+Usage: $0 COMMAND [OPTIONS]
+
+Commands:
+  all                   handle vendor, tailwind
+  vendor                download and verify vendor files
+  tailwind [--watch]    build tailwind.css
+
+EOF
+exit 1
+}
+
+D3JS_URL="https://cdnjs.cloudflare.com/ajax/libs/d3/7.8.5/d3.min.js"
+D3JS_HASH="d6b03aefc9f6c44c7bc78713679c78c295028fa914319119e5cc4b4954855b1c"
+
+__vendor() {
+    URL="$1"
+    OUT="$(basename "$URL")"
+    HASH="$2"
+    if [ -e "$OUT" ]; then
+        echo -n "$HASH  $OUT" | sha256sum --strict --check -
+        return 0
+    fi
+    curl -qs $URL -o $OUT.tmp
+    echo -n "$HASH  $OUT.tmp" | sha256sum --strict --check -
+    mv $OUT.tmp $OUT
+}
+
+_vendor() {
+    command -v curl >/dev/null || fatal "curl not found"
+    command -v sha256sum >/dev/null || fatal "sha256sum not found"
+    __vendor "$D3JS_URL" "$D3JS_HASH"
+}
+
+_tailwind() {
+    # tailwindcss v3.1.6
+    OPTS="$@"
+    command -v tailwindcss >/dev/null || fatal "tailwindcss not found"
+    [ -e "tailwind.input.css" ] || fatal "tailwind.input.css not found"
+    [ -e "tailwind.config.js" ] || fatal "tailwind.config.js not found"
+    tailwindcss $OPTS --minify -i tailwind.input.css -o tailwind.css
+}
+
+main() {
+    cd $(dirname $(realpath $0))
+    case $1 in
+        ""|-h|--help|help)      usage;;
+        all)                    _vendor; _tailwind;;
+        vendor)                 _vendor;;
+        tailwind)               shift; _tailwind $@;;
+        *)                      fatal "unrecognized command: $1";;
+    esac
+}
+
+main "$@"