package .bin/ scripts as proper nix packages, delete .bin/

Packaged 14 scripts from .bin/ into packages/ with proper dependency
declarations (writers.writeDashBin/writeBashBin/writePython3Bin):
- 256color → two56color (terminal color chart)
- avesta.sed → avesta (Avestan transliteration)
- bvg.sh → bvg (Berlin transit disruptions)
- unicode → charinfo (Unicode character info)
- chunk-pdf → chunk-pdf (split PDFs by page count)
- csv2json → csv2json (CSV to JSON converter)
- fix-sd.sh → fix-sd (exFAT SD card recovery, improved output handling)
- json2csv → json2csv (JSON to CSV converter)
- mp3player-write → mp3player-write (audio conversion for MP3 players)
- mushakkil.sh → mushakkil (Arabic diacritization)
- nix-haddock-index → nix-haddock-index (GHC Haddock index generator)
- pdf-ocr.sh → pdf-ocr (OCR PDFs via tesseract)
- prospekte.sh → prospekte (German supermarket flyer browser)
- readme → readme (GitHub README as man page)

All added to overlay and packages output. .bin/ directory removed.

packages/bvg.nix

@@ -0,0 +1,53 @@
+# Berlin BVG transit disruption checker
+{
+  writers,
+  curl,
+  jq,
+}:
+writers.writeDashBin "bvg" ''
+  interesting="U6 N6 140 M46 184 N84"
+
+  ${curl}/bin/curl -sSL 'https://www.bvg.de/disruption-reports/q' \
+    --data-raw '{"variables":{},"query":"{
+      allDisruptions {
+        disruptions {
+          meldungsId
+          linie
+          verkehrsmittel
+          __typename
+          ... on Traffic {
+            datum
+            gueltigVonDatum
+            gueltigVonZeit
+            gueltigBisDatum
+            gueltigBisZeit
+            richtungName
+            richtungHafasId
+            beginnAbschnittName
+            beginnAbschnittHafasId
+            endeAbschnittName
+            endeAbschnittHafasId
+            textIntUrsache
+            sev
+            textIntAuswirkung
+            umfahrung
+            textWAPSMSUrsache
+            textWAPSMSAuswirkung
+            prioritaet
+            __typename
+          }
+        }
+        __typename
+      }
+    }"}' \
+    | ${jq}/bin/jq --arg interesting "$interesting" '
+      .data.allDisruptions.disruptions
+      | map(select(
+        (.linie as $linie
+        | $interesting
+        | split(" ")
+        | index($linie))
+        and (.["__typename"] == "Traffic")
+      ))
+    '
+''