feat(deps): papaparse for expense CSV export

Replaces the hand-rolled `[fields].map(v => \`"\${v}"\`).join(',')`
pattern in expense-export.tsx with papaparse's Papa.unparse.

The previous version didn't handle:
- commas inside fields (would split rows mid-record)
- newlines inside fields (would terminate rows early)
- BOM for Excel-friendly encoding
- numeric/null normalization

Papa.unparse handles all of those + accepts a keyed-object row shape
that lets us define column order and get matching headers for free.

Verified: tsc clean, vitest 1315/1315.

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

pnpm-lock.yaml

@@ -190,6 +190,9 @@ importers:
       p-limit:
         specifier: ^7.3.0
         version: 7.3.0
+      papaparse:
+        specifier: ^5.5.3
+        version: 5.5.3
       pdf-lib:
         specifier: ^1.17.1
         version: 1.17.1
@@ -311,6 +314,9 @@ importers:
       '@types/nodemailer':
         specifier: ^8.0.0
         version: 8.0.0
+      '@types/papaparse':
+        specifier: ^5.5.2
+        version: 5.5.2
       '@types/react':
         specifier: ^19.2.14
         version: 19.2.14
@@ -3147,6 +3153,9 @@ packages:
   '@types/nodemailer@8.0.0':
     resolution: {integrity: sha512-fyf8jWULsCo0d0BuoQ75i6IeoHs47qcqxWc7yUdUcV0pOZGjUTTOvwdG1PRXUDqN/8A64yQdQdnA2pZgcdi+cA==}
 
+  '@types/papaparse@5.5.2':
+    resolution: {integrity: sha512-gFnFp/JMzLHCwRf7tQHrNnfhN4eYBVYYI897CGX4MY1tzY9l2aLkVyx2IlKZ/SAqDbB3I1AOZW5gTMGGsqWliA==}
+
   '@types/parse-json@4.0.2':
     resolution: {integrity: sha512-dISoDXWWQwUquiKsyZ4Ng+HX2KsPL7LyHKHQwgGFEA3IaKac4Obd+h2a/a6waisAoepJlBcx9paWqjA8/HVjCw==}
 
@@ -5776,6 +5785,9 @@ packages:
   pako@1.0.11:
     resolution: {integrity: sha512-4hLB8Py4zZce5s4yd9XzopqwVv/yGNhV1Bl8NTmCq1763HeK2+EwVTv+leGeL13Dnh2wfbqowVPXCIO0z4taYw==}
 
+  papaparse@5.5.3:
+    resolution: {integrity: sha512-5QvjGxYVjxO59MGU2lHVYpRWBBtKHnlIAcSe1uNFCkkptUh63NFRj0FJQm7nR67puEruUci/ZkjmEFrjCAyP4A==}
+
   parent-module@1.0.1:
     resolution: {integrity: sha512-GQ2EWRpQV8/o+Aw8YqtfZZPfNRWZYkbidE9k5rpl/hC3vtHHBfGm2Ifi6qWV+coDGkrUKZAxE3Lot5kcsRlh+g==}
     engines: {node: '>=6'}
@@ -9797,6 +9809,10 @@ snapshots:
     dependencies:
       '@types/node': 20.19.41
 
+  '@types/papaparse@5.5.2':
+    dependencies:
+      '@types/node': 20.19.41
+
   '@types/parse-json@4.0.2': {}
 
   '@types/pdfkit@0.17.6':
@@ -12516,6 +12532,8 @@ snapshots:
 
   pako@1.0.11: {}
 
+  papaparse@5.5.3: {}
+
   parent-module@1.0.1:
     dependencies:
       callsites: 3.1.0