feat(storage): support deleting backends and improve admin UI

- Implement storage backend deletion, which automatically resets default storage settings and user-specific overrides when a backend is removed.
- Add unit tests covering the delete action and its cleanup side effects.
- Improve admin UI responsiveness, fixing table scrolling, flex wrapping, and text truncation for long storage backend names.
- Update security documentation to clarify trusted proxy configurations and explain how trusted proxies are protected from automatic bans.

backend/static/css/00-base.css

@@ -58,6 +58,69 @@
   --surface-2: rgba(39, 39, 42, 0.28);
 }
 
+:root[data-theme="gruvbox"] {
+  color-scheme: dark;
+  --background: #1d2021;
+  --foreground: #ebdbb2;
+  --card: #282828;
+  --card-foreground: #ebdbb2;
+  --muted: #32302f;
+  --muted-foreground: #bdae93;
+  --accent: #3c3836;
+  --accent-foreground: #fbf1c7;
+  --border: rgba(235, 219, 178, 0.18);
+  --input: rgba(235, 219, 178, 0.24);
+  --primary: #d79921;
+  --primary-foreground: #1d2021;
+  --primary-hover: #fabd2f;
+  --ring: #fe8019;
+  --success: #b8bb26;
+  --danger: #fb4934;
+  --radius: 0.65rem;
+  --shadow: 0 24px 70px rgba(0, 0, 0, 0.42);
+  --font-sans: "Inter", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
+  --header-bg: rgba(29, 32, 33, 0.86);
+  --body-bg:
+    radial-gradient(circle at 20% -8%, rgba(215, 153, 33, 0.2), transparent 28rem),
+    radial-gradient(circle at 85% 8%, rgba(184, 187, 38, 0.12), transparent 26rem),
+    linear-gradient(180deg, #1d2021 0%, #181a1b 100%);
+  --surface-1: rgba(235, 219, 178, 0.06);
+  --surface-1-hover: rgba(235, 219, 178, 0.11);
+  --surface-2: rgba(251, 241, 199, 0.04);
+}
+
+:root[data-theme="cyberpunk"] {
+  color-scheme: dark;
+  --background: #08070d;
+  --foreground: #fff36f;
+  --card: #16131f;
+  --card-foreground: #fff36f;
+  --muted: #251d34;
+  --muted-foreground: #9bfaff;
+  --accent: #332246;
+  --accent-foreground: #fff36f;
+  --border: rgba(255, 242, 0, 0.24);
+  --input: rgba(0, 240, 255, 0.34);
+  --primary: #fff200;
+  --primary-foreground: #08070d;
+  --primary-hover: #00f0ff;
+  --ring: #ff2a6d;
+  --success: #00ff9f;
+  --danger: #ff2a6d;
+  --radius: 0.35rem;
+  --shadow: 0 24px 70px rgba(255, 42, 109, 0.16), 0 0 34px rgba(0, 240, 255, 0.12);
+  --font-sans: "Inter", "Rajdhani", "Orbitron", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
+  --header-bg: rgba(8, 7, 13, 0.86);
+  --body-bg:
+    radial-gradient(circle at 10% -10%, rgba(255, 242, 0, 0.2), transparent 26rem),
+    radial-gradient(circle at 90% 8%, rgba(0, 240, 255, 0.18), transparent 26rem),
+    radial-gradient(circle at 45% 110%, rgba(255, 42, 109, 0.18), transparent 30rem),
+    linear-gradient(180deg, #08070d 0%, #120b1a 100%);
+  --surface-1: rgba(0, 240, 255, 0.07);
+  --surface-1-hover: rgba(255, 242, 0, 0.12);
+  --surface-2: rgba(255, 42, 109, 0.06);
+}
+
 :root[data-theme="retro"] {
   color-scheme: light;
   --background: #ffffff;
@@ -98,6 +161,7 @@ html {
   font-family: var(--font-sans);
   background: var(--background);
   color: var(--foreground);
+  overflow-x: clip;
 }
 
 body {
@@ -107,12 +171,27 @@ body {
   display: flex;
   flex-direction: column;
   background: var(--body-bg);
+  overflow-x: clip;
+}
+
+@supports not (overflow-x: clip) {
+  html,
+  body {
+    overflow-x: hidden;
+  }
 }
 
 a {
   color: inherit;
 }
 
+img,
+video,
+canvas,
+iframe {
+  max-width: 100%;
+}
+
 svg {
   width: 1rem;
   height: 1rem;
@@ -176,10 +255,18 @@ svg {
 }
 
 .brand {
+  min-width: 0;
   font-weight: 650;
   text-decoration: none;
 }
 
+.brand > span:last-child {
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
 .brand-mark {
   width: 1.75rem;
   height: 1.75rem;
@@ -312,12 +399,15 @@ label span {
 
 input,
 select,
+textarea,
 button {
   font: inherit;
+  max-width: 100%;
 }
 
 input,
-select {
+select,
+textarea {
   width: 100%;
   min-height: 2.25rem;
   border: 1px solid var(--input);
@@ -354,6 +444,8 @@ input:disabled {
 
 .button,
 button {
+  min-width: 0;
+  max-width: 100%;
   min-height: 2.25rem;
   display: inline-flex;
   align-items: center;
@@ -372,6 +464,14 @@ button {
   cursor: pointer;
 }
 
+.button > span,
+button > span {
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
 .button-primary {
   background: var(--primary);
   color: var(--primary-foreground);
@@ -433,6 +533,8 @@ pre code {
 .badge {
   display: inline-flex;
   align-items: center;
+  max-width: 100%;
+  min-width: 0;
   min-height: 1.5rem;
   border-radius: 999px;
   background: var(--muted);
@@ -440,6 +542,9 @@ pre code {
   padding: 0.2rem 0.6rem;
   font-size: 0.75rem;
   font-weight: 600;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
 }
 
 .sr-only {