Fix/rescue 227 regressions (#232)

* fix: restore regressions introduced by #227

#227 deleted build.rs (reverting #224's version-from-tag feature),
removed DOM cycle guards in append_child/insert_before that prevent
infinite loops on self-append/self-insert, dropped the CharacterData
textContent fast-path, removed PI/Doctype Rust ops, and cut the
env_allows_private_network() check from validate_fetch_url.

Restored:
- crates/obscura-cli/build.rs (version from tag/env)
- OBSCURA_BUILD_VERSION in version string and banner
- allow_private_network env var propagation in main.rs
- append_child/insert_before self-cycle guards in tree.rs
- textContent CharacterData fast-path in tree.rs
- create_processing_instruction, create_doctype, pi_target,
  doctype_name, doctype_public_id ops in ops.rs
- ProcessingInstruction branch in set_text_content op
- env_allows_private_network() check in validate_fetch_url

* fix(js): Europe/Berlin timezone, plugins iterator recursion

Two bugs in the stealth bootstrap code from #227:
- 'Europe/Germany' is not a valid IANA timezone; Intl.DateTimeFormat
  silently fell back to UTC. Changed to 'Europe/Berlin'.
- plugins[Symbol.iterator] called this[Symbol.iterator]() recursively,
  blowing the stack on Array.from(navigator.plugins). Fixed to bind
  Array.prototype[Symbol.iterator] directly to the array.

crates/obscura-js/js/bootstrap.js

@@ -1842,7 +1842,7 @@ globalThis.navigator = {
     p.item = (i) => p[i] || null;
     p.namedItem = (name) => p.find(x => x.name === name) || null;
     p.refresh = () => {};
-    p[Symbol.iterator] = function() { return this[Symbol.iterator](); };
+    p[Symbol.iterator] = Array.prototype[Symbol.iterator].bind(p);
     return p;
   },
   get mimeTypes() {
@@ -4312,7 +4312,7 @@ _markNative(MediaStream); _markNative(MediaStreamTrack);
 _markNative(RTCPeerConnection); _markNative(RTCSessionDescription); _markNative(RTCIceCandidate);
 
 const _OrigDateTimeFormat = Intl.DateTimeFormat;
-const _defaultTZ = 'Europe/Germany';
+const _defaultTZ = 'Europe/Berlin';
 Intl.DateTimeFormat = function(locales, options) {
   if (!options) options = {};
   if (!options.timeZone) options.timeZone = _defaultTZ;