feat(vcard): add RFC 6868 parameter value encoding

Adds application/adapters/param_encoding.rs: encode/decode for the three
RFC 6868 caret-escape sequences (^n newline, ^^ literal caret, ^' literal
DQUOTE) plus render_param_value, which quotes and encodes a parameter
value only when the vCard/iCalendar param-value grammar requires it
(comma/semicolon/colon triggers quoting; an embedded DQUOTE/caret/newline
needs escaping even once quoted).

Wires render_param_value into the two vCard generators' TYPE parameter
emission (EMAIL/TEL/ADR) in carddav_adapter.rs::contact_to_vcard and
contact_service.rs::generate_vcard — contact `type` fields are free text,
not a fixed enum, so a value containing a comma or quote previously
produced outright broken vCard syntax (no quoting/escaping was applied
at all).

Scope note: this branch only fixes the generation side. The existing
vCard parser is a naive line-by-line substring scanner (`line.contains
("TYPE=WORK")`) with no real per-parameter tokenizing, so there's no
integration point yet for the decode half without a larger parser
rewrite — that's part of the vCard 4.0 work (RFC 6350), which depends on
this branch for the shared encoding utility.

src/application/adapters/mod.rs

@@ -2,6 +2,7 @@
 
 pub mod caldav_adapter;
 pub mod carddav_adapter;
+pub mod param_encoding;
 pub mod plugin_lifecycle_hook;
 pub mod plugin_user_lifecycle_hook;
 pub mod webdav_adapter;