fix: version display, FileBrowser auto-login, nostr relay, UID mappings

Version per build:
- Health endpoint returns "1.2.0-alpha-{git_hash}" using GIT_HASH env
- CI passes git hash to cargo build

FileBrowser auto-login:
- filebrowser-client.ts: include CSRF token + credentials:include
- First-boot: generate random password, store at secrets/filebrowser/
- Set FileBrowser admin password to match after container creation

Nostr relay:
- Use docker.io/scsibug/nostr-rs-relay:0.9.0 (not in our registry)

UID mappings:
- Added electrumx (UID 1000), mysql-mempool, archy-btcpay-db, nextcloud-db

522 tests pass, Rust compiles clean.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-iso-dev.yml

@@ -26,6 +26,7 @@ jobs:
       - name: Build backend
         run: |
           source $HOME/.cargo/env 2>/dev/null || true
+          export GIT_HASH=$(git rev-parse --short HEAD)
           cargo build --release --manifest-path core/Cargo.toml
 
       - name: Build frontend