Initial implementation: extend TrueCloud Backup to S3 and B2 providers

Patches middlewared at runtime via sitecustomize.py (no file edits to /usr/)
and widens the UI credential dropdown from Storj-only to S3+B2+Storj.
Persists across TrueNAS updates via PREINIT initshutdownscript stored in DB.

patch/patch_ui.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+"""
+Patches the TrueNAS webui Angular bundle to show S3 and B2 credentials
+in the TrueCloud Backup task form, instead of Storj only.
+
+The compiled bundle contains:
+    "filterByProviders",["STORJ_IX"]
+which is the template binding [filterByProviders]="[CloudSyncProviderName.Storj]".
+We replace the array with ["STORJ_IX","S3","B2"] so all three providers appear.
+
+Run automatically by apply.sh on every boot. Safe to run multiple times.
+"""
+
+import os
+import re
+import shutil
+import sys
+
+WEBUI_CANDIDATES = [
+    "/usr/share/truenas/webui",
+    "/usr/share/truenas-ui",
+    "/var/www/truenas",
+]
+
+# The pattern as compiled by Angular's Ivy into minified JS.
+# String literals survive minification; the function name before the comma
+# is mangled and not part of our match.
+FIND = re.compile(r'("filterByProviders",)\["STORJ_IX"\]')
+REPLACE = r'\1["STORJ_IX","S3","B2"]'
+
+# Presence of this string means we already patched this file.
+MARKER = '"STORJ_IX","S3","B2"'
+
+
+def find_webui():
+    for d in WEBUI_CANDIDATES:
+        if os.path.isdir(d):
+            return d
+    return None
+
+
+def find_bundle(webui):
+    for root, _, names in os.walk(webui):
+        for name in names:
+            if not name.endswith(".js"):
+                continue
+            path = os.path.join(root, name)
+            try:
+                with open(path) as fh:
+                    content = fh.read()
+                if FIND.search(content):
+                    return path, content
+            except (UnicodeDecodeError, PermissionError, OSError):
+                continue
+    return None, None
+
+
+def main():
+    webui = find_webui()
+    if not webui:
+        print("[truecloud-patch] WARNING: webui directory not found, skipping UI patch")
+        sys.exit(0)
+
+    path, content = find_bundle(webui)
+    if path is None:
+        print(
+            "[truecloud-patch] WARNING: filterByProviders pattern not found in webui bundle.\n"
+            "[truecloud-patch] The UI patch may need updating for this TrueNAS version.\n"
+            "[truecloud-patch] File an issue at https://github.com/sudolulo/truenas-truecloud-patch"
+        )
+        sys.exit(0)
+
+    if MARKER in content:
+        print(f"[truecloud-patch] UI already patched: {path}")
+        sys.exit(0)
+
+    backup = path + ".pre-truecloud-patch"
+    if not os.path.exists(backup):
+        shutil.copy2(path, backup)
+
+    patched, count = FIND.subn(REPLACE, content)
+    with open(path, "w") as fh:
+        fh.write(patched)
+
+    print(f"[truecloud-patch] UI bundle patched ({count} replacement(s)): {path}")
+
+
+if __name__ == "__main__":
+    main()