Normalize frontmatter taxonomy across 293 document transcriptions

Categories now match folder names (15 canonical values).
Types normalized to 25 canonical values per VAULT_MAP.md spec.
Context-aware mapping: W-2s→tax-form, lease files→lease, vet records→vet, etc.

documents/travel/customs_declaration/customs_jiang_xianlu.md

@@ -1,6 +1,6 @@
 ---
-type: travel document
-category: customs declaration form
+type: travel-doc
+category: travel
 person: Jiang Xianlu
 date: 
 source: customs_jiang_xianlu.jpg

documents/travel/customs_declaration/customs_xue_fengqin.md

@@ -1,6 +1,6 @@
 ---
-type: travel document
-category: customs declaration form
+type: travel-doc
+category: travel
 person: Xue Fengqin
 date: 
 source: customs_xue_fengqin.jpg

documents/travel/customs_declaration/海关申报表.md

@@ -1,6 +1,6 @@
 ---
-type: travel document
-category: customs declaration form
+type: travel-doc
+category: travel
 person: Jiang Xianlu, Xue Fengqin
 date: 
 source: 海关申报表.pdf