v0.2.0 — pre-beta: per-MAC bindings, /metrics, themes, animated forge

This is the bulk pre-beta cleanup pass. Bumps the workspace to 0.2.0.
Test count is 56 -> 66 (+10), clippy is fully clean across the
workspace (was several dozen warnings).

## New features

**Per-MAC host bindings** (Tinkerbell smee pattern). New
`HostBindings` registry maps a MAC -> preferred boot target, persisted
to <work_dir>/hosts.json. The DHCP reply now embeds `?mac=${mac}` in
the boot.ipxe URL; iPXE substitutes the literal MAC client-side, so
the HTTP layer can short-circuit straight to the bound target instead
of rendering the menu. Reserved menu shortcuts (`_local`, `_gate`,
`_tools_menu`) are valid targets too. New /api/hosts CRUD + a Hosts
tab in the sidebar.

**Prometheus `/metrics`** endpoint. Tiny lock-free implementation —
just AtomicU64s and a Display impl, no `prometheus` / `metrics-rs`
dep. Counters: DHCP replies (per arch label), DHCP declined, TFTP
transfers (per status), TFTP bytes, HTTP requests (per route).
Gauges: ISO count, client count, gate count, gate-imaging, NFS active
mounts, uptime, build info. Plain text exposition format,
text/plain;version=0.0.4 content-type, no auth (all metric values are
non-sensitive counts).

**Light + dark themes**. CSS tokens on `:root` and
`:root[data-theme=light]`, swap by toggle button (top-right) or `T`
hotkey. Persisted in localStorage; pre-paint inline script avoids
dark<->light flash. Light palette designed against the Netbox Labs
reference screenshot — near-white surfaces, soft grey dividers,
accent unchanged for brand consistency. Terminal pane stays dark in
both themes (it's a console, that's the right read).

**Animated SVG logo + forge widget**. New `logo.svg` is a refined
silver/grey anvil. New `anvil-forge.svg` adds rising sparks and a
pulsing underglow via SMIL — pure SVG, no GIF, no JS animation loop.
Used:
  - in the **forge progress** widget on Dashboard + Forge Gate, paired
    with a `linear-gradient(warn -> accent)` bar with a moving sheen;
    goes idle (greyscale, no sheen) at zero imaging load
  - in the page-load `<div class=loader>` that replaces the old
    "Loading..." text

## Code cleanup pass

`cargo clippy --workspace --all-targets` is now warning-free. Spot
fixes across the tree:
  - `format!()`-into-`String` -> `std::fmt::Write::write!`
  - manual reverse comparators -> `Reverse`
  - `map_or(false, ...)` -> `is_some_and`
  - redundant closures -> method references
  - `r#"..."#` raw strings without `"` -> `r"..."`
  - `std::io::Error::new(Other, ...)` -> `Error::other`
  - `as i32` on `c.id()` -> `cast_signed()`
  - merged identical match arms

## Windows workflow validation

New integration test synthesizes an ISO9660 with the SOURCES\\BOOT.WIM
sentinel, uploads it, asserts:
  1. introspection labels it `windows_pe` with has_boot_wim=true,
  2. the boot entry is `BootKind::Wimboot` with all five canonical
     files (bootmgr, bootmgr.efi, bcd, boot.sdi, boot.wim),
  3. the rendered iPXE script chains wimboot with `initrd --name`
     entries for each file, and
  4. NO trust-store strings appear in the rendered output: bcdedit,
     testsigning, certutil, httpdisk, and test-signed are all
     explicitly forbidden as a hard guarantee.

WinPE bootstrap (startnet.cmd) picks up the Bootimus v0.1.58 lessons:
explicit `net start Workstation` before `net use` to avoid the SMB
client lazy-init race, and surfaces errors instead of blind retries.

## Docs

architecture.md gains a "Phase 5" section explaining the host-bindings
+ metrics + theming + Windows-test work, plus a refreshed "deferred
to Phase 6" list (real-hardware integration, autounattend library,
distro profile manifest, WoL trigger, syslog receiver, IPv6).
README updates the status line, the "what it does" list, and adds
the new Hosts/Terminal tab names.

crates/iso-store/src/smb.rs

@@ -87,13 +87,17 @@ impl SmbManager {
     /// Write out `smb.conf` for the currently-discovered shares. Safe to
     /// call while smbd is running — smbd reloads on SIGHUP.
     pub fn write_conf(&self) -> std::io::Result<Vec<String>> {
+        use std::fmt::Write as _;
         std::fs::create_dir_all(&self.smb_dir)?;
         let shares = self.discover_shares();
         let mut conf = String::new();
         conf.push_str(SMB_CONF_GLOBAL);
         for name in &shares {
             let path = self.smb_dir.join(name);
-            conf.push_str(&format!(
+            // Per-share block. `write!` to String never fails — the unwrap
+            // is provably unreachable, but expect() makes that explicit.
+            write!(
+                conf,
                 "\n[{name}]\n\
                  path = {}\n\
                  comment = PXEForge Windows install media ({name})\n\
@@ -103,7 +107,8 @@ impl SmbManager {
                  browseable = yes\n\
                  available = yes\n",
                 path.display(),
-            ));
+            )
+            .expect("writing to a String is infallible");
         }
         let tmp = self.conf_path.with_extension("conf.tmp");
         std::fs::write(&tmp, conf)?;
@@ -114,7 +119,7 @@ impl SmbManager {
     /// Start smbd. No-op if already running.
     pub fn start(&self) -> SmbState {
         let mut g = self.child.lock();
-        if g.as_ref().map_or(false, |c| c.id() > 0) {
+        if g.as_ref().is_some_and(|c| c.id() > 0) {
             return self.state.lock().clone();
         }
         if !smbd_present() {
@@ -173,7 +178,10 @@ impl SmbManager {
             }
         };
         if let Some(c) = g.as_mut() {
-            let pid = c.id() as i32;
+            // u32 -> i32 for libc::kill. We never spawn enough children
+            // for the pid to overflow i32; cast_signed makes the intent
+            // explicit and silences the lint.
+            let pid = c.id().cast_signed();
             // SAFETY: libc::kill is FFI-safe; we pass a pid we own (returned
             // from `Child::id` above, the child is alive because we hold the
             // Mutex guard `g`) and a well-defined signal constant. Return
@@ -211,7 +219,7 @@ fn smbd_present() -> bool {
     false
 }
 
-const SMB_CONF_GLOBAL: &str = r#"[global]
+const SMB_CONF_GLOBAL: &str = r"[global]
 workgroup = PXEFORGE
 server min protocol = SMB2
 smb ports = 445
@@ -227,7 +235,7 @@ lock directory = /tmp
 state directory = /tmp
 cache directory = /tmp
 pid directory = /tmp
-"#;
+";
 
 /// Extract a Windows ISO at `iso_path` into `smb_dir/<slug>/`. Uses
 /// `7z` when available (most reliable for UDF + ISO9660 hybrid images);
@@ -271,10 +279,10 @@ pub fn extract_windows_iso(iso_path: &Path, smb_dir: &Path, slug: &str) -> std::
             .arg(&target)
             .output()?;
         if out.status.success() { return Ok(target); }
-        return Err(std::io::Error::new(
-            std::io::ErrorKind::Other,
-            format!("bsdtar failed: {}", String::from_utf8_lossy(&out.stderr)),
-        ));
+        return Err(std::io::Error::other(format!(
+            "bsdtar failed: {}",
+            String::from_utf8_lossy(&out.stderr)
+        )));
     }
     Err(std::io::Error::new(
         std::io::ErrorKind::NotFound,