refactor: move buildable .NET source into src/, update CI/doc paths

Groups the repo root into src (buildable source), docs (already existed),
and everything else (db/, scripts/, tests/, deploy/ - deployment/ops/test
assets that aren't compiled, already organized as their own folders). CI
now only needs src/ to build: dotnet restore/build/test/publish all point
at src/TaxBaik.sln, src/TaxBaik.Web/, src/TaxBaik.Proxy/.

- git mv every project (Domain, Infrastructure, Application,
  Application.Tests, Web, Web.Client, Proxy) and TaxBaik.sln into src/ as a
  unit, so relative ProjectReference/.sln paths stay valid unchanged.
- .gitea/workflows/deploy.yml: 6 dotnet restore/clean/build/test/publish
  invocations now point at src/. db/migrations and scripts/ stay at root
  (deploy_gb.sh and browser-e2e.yml only touch published output and the
  deployed URL, not source paths - verified, no changes needed there).
- scripts/validate_admin_render.sh: admin render-mode file paths now
  src/TaxBaik.Web.Client/...
- scripts/validate_kst_timestamps.sh: dropped deploy.sh from its target
  list - that script was removed in the prior cleanup commit (dead, no
  CI workflow referenced it) but this validator still expected it to exist.
- CLAUDE.md, docs/ENGINEERING_HARNESS.md, docs/ADMIN_PATTERN_CRITIQUE_WBS.md:
  updated project-structure diagram, dotnet run/build commands, and grep
  targets to the new src/ paths (also fixed a pre-existing stale path in
  ADMIN_PATTERN_CRITIQUE_WBS.md that still said TaxBaik.Web/Components/Admin
  from before that ever moved to TaxBaik.Web.Client).
- Added a Repo Root harness rule + Architecture Guardrail entries: new files
  belong under src/docs/tests/scripts/db/deploy, not loose at root; temp
  work stays outside the repo (or under a gitignored .scratch/) and is
  never committed.

Verified locally: dotnet build/test src/TaxBaik.sln (26/26 tests), and all
three scripts/validate_*.sh pass against the new layout.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

TaxBaik.Web/Pages/Shared/_Footer.cshtml

@@ -1,33 +0,0 @@
-<footer class="bg-light border-top mt-5 py-4">
-    <div class="container">
-        <div class="row g-4">
-            <div class="col-md-4">
-                <h6 class="fw-bold">백원숙 세무회계</h6>
-                <p class="small text-muted">
-                    사업자 기장, 부동산 양도세·증여세,<br />
-                    종합소득세 전문 상담
-                </p>
-            </div>
-            <div class="col-md-4">
-                <h6 class="fw-bold">연락처</h6>
-                <p class="small">
-                    📞 <a href="tel:010-4122-8268" class="text-decoration-none">010-4122-8268</a><br />
-                    📧 <a href="mailto:taxbaik5668@gmail.com" class="text-decoration-none">taxbaik5668@gmail.com</a>
-                </p>
-            </div>
-            <div class="col-md-4">
-                <h6 class="fw-bold">채널</h6>
-                <p class="small">
-                    <a href="http://pf.kakao.com/_xoxchTX" target="_blank" class="btn btn-sm btn-warning me-2">카카오톡</a>
-                    <a href="https://www.instagram.com/taxtory5668/" target="_blank" class="btn btn-sm btn-outline-secondary">Instagram</a>
-                </p>
-            </div>
-        </div>
-        <hr class="my-3" />
-        <div class="text-center small text-muted">
-            <p>© 2026 백원숙 세무회계. All rights reserved.</p>
-            <a href="/taxbaik/privacy" class="text-decoration-none text-muted me-2">개인정보처리방침</a>
-            <a href="/taxbaik/terms" class="text-decoration-none text-muted">이용약관</a>
-        </div>
-    </div>
-</footer>

TaxBaik.Web/Pages/Shared/_Header.cshtml

@@ -1,34 +0,0 @@
-<header class="sticky-top bg-white border-bottom site-header">
-    <nav class="navbar navbar-expand-lg navbar-light container-fluid px-3 py-2">
-        <a class="navbar-brand fw-bold" href="/taxbaik">
-            <span class="text-primary">백원숙</span> 세무회계
-        </a>
-        <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
-            <span class="navbar-toggler-icon"></span>
-        </button>
-        <div class="collapse navbar-collapse mt-3 mt-lg-0" id="navbarNav">
-            <ul class="navbar-nav ms-auto gap-2 align-items-lg-center">
-                <li class="nav-item">
-                    <a class="nav-link" href="/taxbaik">홈</a>
-                </li>
-                <li class="nav-item">
-                    <a class="nav-link" href="/taxbaik/about">소개</a>
-                </li>
-                <li class="nav-item">
-                    <a class="nav-link" href="/taxbaik/services">서비스</a>
-                </li>
-                <li class="nav-item">
-                    <a class="nav-link" href="/taxbaik/blog">블로그</a>
-                </li>
-                <li class="nav-item">
-                    <a class="btn btn-primary btn-sm ms-lg-2 w-100 w-lg-auto" href="/taxbaik/contact">상담신청</a>
-                </li>
-            </ul>
-        </div>
-        <div class="ms-3 d-none d-md-block">
-            <a href="tel:010-4122-8268" class="text-decoration-none text-dark fw-500">
-                📞 010-4122-8268
-            </a>
-        </div>
-    </nav>
-</header>

TaxBaik.Web/Pages/Shared/_ViewImports.cshtml

@@ -1,3 +0,0 @@
-@using TaxBaik.Web
-@namespace TaxBaik.Web.Pages
-@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers

TaxBaik.Web/Pages/Shared/_ViewStart.cshtml

@@ -1,3 +0,0 @@
-@{
-    Layout = "_Layout";
-}