docs: add architecture and veins documentation

- System overview, artery hierarchy, build flow, room config diagrams
- Veins docs: Jira, Slack, Google OAuth
- Shunts docs: MercadoPago mock
- DOT source files with generated SVGs
- HTML viewers with navigation and full-screen mode

Solves:
- Freelance work standardization
- Missing infrastructure replication (shunts)
- Reliable testing environment (BDD -> Gherkin -> Tests)

docs/veins/jira.dot

@@ -0,0 +1,53 @@
+digraph JiraVein {
+    rankdir=LR;
+    compound=true;
+    fontname="Helvetica";
+    node [fontname="Helvetica", fontsize=11, shape=box, style="rounded,filled"];
+    edge [fontname="Helvetica", fontsize=10];
+
+    labelloc="t";
+    label="Jira Vein - API Flow";
+    fontsize=16;
+
+    // Client
+    subgraph cluster_client {
+        label="Soleprint";
+        style=filled;
+        color="#E8F5E9";
+        fillcolor="#E8F5E9";
+
+        app [label="Application", fillcolor="#C8E6C9"];
+        vein [label="Jira Vein\n(artery/veins/jira)", fillcolor="#A5D6A7"];
+    }
+
+    // Auth
+    subgraph cluster_auth {
+        label="Authentication";
+        style=filled;
+        color="#FFF8E1";
+        fillcolor="#FFF8E1";
+
+        token [label="API Token\n(Basic Auth)", fillcolor="#FFECB3"];
+    }
+
+    // Jira API
+    subgraph cluster_jira {
+        label="Jira Cloud API";
+        style=filled;
+        color="#E3F2FD";
+        fillcolor="#E3F2FD";
+
+        issues [label="/rest/api/3/issue", fillcolor="#BBDEFB"];
+        search [label="/rest/api/3/search", fillcolor="#BBDEFB"];
+        projects [label="/rest/api/3/project", fillcolor="#BBDEFB"];
+        transitions [label="/rest/api/3/issue/{id}/transitions", fillcolor="#BBDEFB"];
+    }
+
+    // Flow
+    app -> vein [label="get_issue()"];
+    vein -> token [label="auth"];
+    token -> issues [label="GET/POST"];
+    token -> search [label="JQL"];
+    token -> projects [label="list"];
+    token -> transitions [label="update status"];
+}