chore: remove tor from startos core

Tor is being moved from a built-in OS feature to a service. This removes
the Arti-based Tor client, onion address management, hidden service
creation, and all related code from the core backend, frontend, and SDK.

- Delete core/src/net/tor/ module (~2060 lines)
- Remove OnionAddress, TorSecretKey, TorController from all consumers
- Remove HostnameInfo::Onion and HostAddress::Onion variants
- Remove onion CRUD RPC endpoints and tor subcommand
- Remove tor key handling from account and backup/restore
- Remove ~12 tor-related Cargo dependencies (arti-client, torut, etc.)
- Remove tor UI components, API methods, mock data, and routes
- Remove OnionHostname and tor patterns/regexes from SDK
- Add v0_4_0_alpha_20 database migration to strip onion data
- Bump version to 0.4.0-alpha.20

sdk/base/lib/util/regexes.ts

@@ -39,10 +39,6 @@ export const localHostname = new ComposableRegex(
   /[-a-zA-Z0-9@:%._\+~#=]{1,256}\.local/,
 )
 
-export const torHostname = new ComposableRegex(
-  /[-a-zA-Z0-9@:%._\+~#=]{1,256}\.onion/,
-)
-
 // https://ihateregex.io/expr/url/
 export const url = new ComposableRegex(
   /https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()!@:%_\+.~#?&\/\/=]*)/,
@@ -52,10 +48,6 @@ export const localUrl = new ComposableRegex(
   /https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.local\b([-a-zA-Z0-9()!@:%_\+.~#?&\/\/=]*)/,
 )
 
-export const torUrl = new ComposableRegex(
-  /https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.onion\b([-a-zA-Z0-9()!@:%_\+.~#?&\/\/=]*)/,
-)
-
 // https://ihateregex.io/expr/ascii/
 export const ascii = new ComposableRegex(/[ -~]*/)