chore(migration): repoint every published link off GitHub

The canonical repo is git.zacharyzhang.com now, so every URL a user can
actually reach had to move with it.

Self-updater: `PRODUCTION_ENDPOINTS.update_base_url` targets Gitea's
`/api/v1/repos/.../releases`, which serves the same wire format GitHub's
releases API did — `Release`/asset deserialisation is unchanged. The alpha
channel requests `?per_page=30&limit=30` because GitHub reads the page size
from `per_page` and Gitea from `limit`, and each ignores the other's, so one
URL stays correct on either.

Installers: same API base, and the documented one-liners become
`https://kigicli.dev/install.{sh,ps1}`. That domain's Worker proxies both
files from Gitea raw `main`, so the published install command survives any
future forge move without being reprinted everywhere. install.ps1 also drops
the GitHub-specific `Accept: application/vnd.github+json`.

Everything else user-facing: `/feedback` and the shell's feedback fallback
point at the Gitea issue tracker, `/docs` at the Gitea-rendered README, and
web_fetch's User-Agent at kigicli.dev. SECURITY.md now routes reports to the
issue tracker with a warning to withhold exploitable detail, because Gitea
has no equivalent of GitHub's private vulnerability reporting. Comments
naming `.github/workflows/release.yml` name `.gitea/` now.

Tests assert against these constants rather than literal URLs, so they
follow automatically; the one URL-shape assertion (production endpoints are
https) still holds.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/codegen/kigi-tui/src/slash/commands/docs.rs

@@ -9,8 +9,9 @@ use crate::docs::{all_titles, find_doc};
 use crate::slash::command::{AppCtx, ArgItem, CommandExecCtx, CommandResult, SlashCommand};
 
 /// Online docs landing page (hardcoded like other TUI deep-links; the
-/// project README is the docs entry point for the GitHub-hosted docs).
-pub const BUILD_DOCS_URL: &str = "https://github.com/ZacharyZhang-NY/Kigi-CLI#readme";
+/// project README is the docs entry point for the repo-hosted docs).
+pub const BUILD_DOCS_URL: &str =
+    "https://git.zacharyzhang.com/ZacharyZhang-NY/Kigi-CLI/src/branch/main/README.md";
 
 /// Open How-to Guides or online Build docs.
 pub struct DocsCommand;

crates/codegen/kigi-tui/src/slash/commands/feedback.rs

@@ -1,12 +1,13 @@
-//! `/feedback` -- open the Kigi GitHub issues page.
+//! `/feedback` -- open the Kigi issues page.
 
 use crate::app::actions::Action;
 use crate::slash::command::{CommandExecCtx, CommandResult, SlashCommand};
 
 /// Where feedback goes: the project's own issue tracker. Kigi is a community
-/// build, so its feedback belongs on its GitHub repo — mirroring the official
+/// build, so its feedback belongs on its own repo — mirroring the official
 /// kimi-cli, whose `/feedback` opens its repo's issues page.
-pub const FEEDBACK_ISSUES_URL: &str = "https://github.com/ZacharyZhang-NY/Kigi-CLI/issues";
+pub const FEEDBACK_ISSUES_URL: &str =
+    "https://git.zacharyzhang.com/ZacharyZhang-NY/Kigi-CLI/issues";
 
 /// Open the Kigi issue tracker in the browser.
 pub struct FeedbackCommand;
@@ -17,7 +18,7 @@ impl SlashCommand for FeedbackCommand {
     }
 
     fn description(&self) -> &str {
-        "Report feedback on the Kigi GitHub issues page"
+        "Report feedback on the Kigi issues page"
     }
 
     fn usage(&self) -> &str {