Rename Castle Accounting extension to Libra

Full identifier rename: module path lnbits.extensions.castle →
lnbits.extensions.libra, DB ext_castle → ext_libra, URL prefix
/castle/ → /libra/, manifest id castle → libra, fava ledger slug
default castle-ledger → libra-ledger, Beancount source metadata
castle-api → libra-api and link prefixes castle-{entry,tx}- →
libra-{entry,tx}-, column castle_wallet_id → libra_wallet_id, all
Python/JS/HTML identifiers (castle_ext, CastleSettings,
castle_reference, castleWalletConfigured, etc.).

Display name "Castle Accounting" → "Libra" (the scales/balance
metaphor — fits double-entry bookkeeping).

No backward compat: production hosts will be force-updated. Old
castle-prefixed Beancount metadata in existing Fava ledgers is
historical; new entries use libra-* prefixes going forward.

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

config.json

@@ -1,11 +1,11 @@
 {
-  "name": "Castle Accounting",
+  "name": "Libra",
   "short_description": "Double-entry accounting system for collective projects",
-  "tile": "/castle/static/image/castle.png",
+  "tile": "/libra/static/image/libra.png",
   "contributors": [
     "Your Name"
   ],
   "hidden": false,
-  "migration_module": "lnbits.extensions.castle.migrations",
-  "db_name": "ext_castle"
+  "migration_module": "lnbits.extensions.libra.migrations",
+  "db_name": "ext_libra"
 }