Rebrand SooSeF to FieldWitness

Complete project rebrand for better positioning in the press freedom
and digital security space. FieldWitness communicates both field
deployment and evidence testimony — appropriate for the target audience
of journalists, NGOs, and human rights organizations.

Rename mapping:
- soosef → fieldwitness (package, CLI, all imports)
- soosef.stegasoo → fieldwitness.stego
- soosef.verisoo → fieldwitness.attest
- ~/.soosef/ → ~/.fwmetadata/ (innocuous data dir name)
- SOOSEF_DATA_DIR → FIELDWITNESS_DATA_DIR
- SoosefConfig → FieldWitnessConfig
- SoosefError → FieldWitnessError

Also includes:
- License switch from MIT to GPL-3.0
- C2PA bridge module (Phase 0-2 MVP): cert.py, export.py, vendor_assertions.py
- README repositioned to lead with provenance/federation, stego backgrounded
- Threat model skeleton at docs/security/threat-model.md
- Planning docs: docs/planning/c2pa-integration.md, docs/planning/gtm-feasibility.md

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

frontends/web/templates/stego/generate.html

@@ -1,6 +1,6 @@
 {% extends "base.html" %}
 
-{% block title %}Generate Credentials - Stegasoo{% endblock %}
+{% block title %}Generate Credentials - Stego{% endblock %}
 
 {% block content %}
 <div class="row justify-content-center" data-page="generate">
@@ -500,7 +500,7 @@
 {% endblock %}
 
 {% block scripts %}
-<script src="{{ url_for('static', filename='js/soosef.js') }}"></script>
+<script src="{{ url_for('static', filename='js/fieldwitness.js') }}"></script>
 <script src="{{ url_for('static', filename='js/generate.js') }}"></script>
 {% if generated %}
 <script>
@@ -508,7 +508,7 @@
 const passphraseWords = '{{ passphrase|default("", true) }}'.split(' ').filter(w => w.length > 0);
 
 function copyPin() {
-    Stegasoo.copyToClipboard(
+    Stego.copyToClipboard(
         '{{ pin|default("", true) }}',
         document.getElementById('pinCopyIcon'),
         document.getElementById('pinCopyText')
@@ -516,7 +516,7 @@ function copyPin() {
 }
 
 function copyPassphrase() {
-    Stegasoo.copyToClipboard(
+    Stego.copyToClipboard(
         '{{ passphrase|default("", true) }}',
         document.getElementById('passphraseCopyIcon'),
         document.getElementById('passphraseCopyText')
@@ -524,11 +524,11 @@ function copyPassphrase() {
 }
 
 function toggleMemoryAid() {
-    StegasooGenerate.toggleMemoryAid(passphraseWords);
+    StegoGenerate.toggleMemoryAid(passphraseWords);
 }
 
 function regenerateStory() {
-    StegasooGenerate.regenerateStory(passphraseWords);
+    StegoGenerate.regenerateStory(passphraseWords);
 }
 </script>
 {% endif %}