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>

docs/BQL-PRICE-NOTATION-SOLUTION.md

@@ -63,7 +63,7 @@ Expenses:Food  -360.00 EUR @@ 337096 SATS
 **Total calculation**: Exact 337,096 SATS (no rounding)
 **Precision**: Preserves exact SATS amount from original calculation
 
-**Why `@@` is better for Castle:**
+**Why `@@` is better for Libra:**
 - ✅ Preserves exact SATS amount (no rounding errors)
 - ✅ Matches current metadata storage exactly
 - ✅ Clearer intent: "this transaction equals X SATS total"
@@ -124,7 +124,7 @@ GROUP BY account;
 ### Step 1: Run Metadata Test
 
 ```bash
-cd /home/padreug/projects/castle-beancounter
+cd /home/padreug/projects/libra-beancounter
 ./test_metadata_simple.sh
 ```
 
@@ -166,7 +166,7 @@ Add one test entry to your ledger:
 
 Then query:
 ```bash
-curl -s "http://localhost:3333/castle-ledger/api/query" \
+curl -s "http://localhost:3333/libra-ledger/api/query" \
   -G \
   --data-urlencode "query_string=SELECT account, position, price_number, price_currency WHERE account ~ 'TEST'" \
   | jq '.'