fix: detect MIPS endianness correctly in install script

Linux's uname -m always reports 'mips' for all MIPS variants regardless
of endianness, causing the installer to download the big-endian binary
for little-endian MIPS routers like the JCG Q20 (MT7621 SoC).

Add a detect_mips_endianness() function that probes:
1. /etc/openwrt_release DISTRIB_ARCH field (covers OpenWrt)
2. /proc/cpuinfo byte order field (generic Linux)
3. readelf ELF header inspection (authoritative fallback)
4. Big-endian as the default fallback (historical convention)

This ensures JCG Q20 and other little-endian MIPS routers get the
correct linux-mipsle / linux-mips64le binary.

Signed-off-by: Galih Tama <galpt@v.recipes>

refactor: achieve near-zero-allocation parsing and eliminate dead code

Replace the parser's allocation-heavy text processing with a
zero-allocation approach:

- Introduce LineScanner: iterates over lines in a raw []byte slice
  without allocating per-line strings (replaces strings.Split/SplitLines)
- Introduce FieldTokenizer: tokenises a string into fields using a
  pre-allocated [64]string buffer on the stack (replaces strings.Fields)
- Replace map-based tier table storage with fixed-size arrays + linear
  scan, eliminating hash-map allocations during parsing
- Replace fmt.Sprintf with formatUint64 writing into a stack buffer
- Replace strings.Split with manual comma scanning in parseSentLine
- Hand-roll ParseUint64 to avoid strconv.ParseUint error-interface
  escape, making it truly zero-allocation (0 B/op, 19 ns/op)
- Remove dead utility functions: SplitLines, Fields, Split, SplitN
- Remove unused util.SplitLines from split.go
- Update README design notes to reflect the new parser architecture
- Add allocation benchmarks to pkg/parser to prevent regression

Results (2-interface CAKE setup):
  Before: 124 allocs/op, 21,232 B/op, 20,545 ns/op
  After:    3 allocs/op,  3,072 B/op,  9,576 ns/op
  97.6% fewer allocations, 85.5% less memory, 53% faster

Signed-off-by: Galih Tama <galpt@v.recipes>

refactor: remove dead code, fix documentation, and improve code quality

- Remove 7 unused functions and their associated imports and vars:
  supportsJSON, parseJSON, AfterSlash, StringToBytes, TrimPrefix,
  TrimRight, getUint
- Remove dead test TestParseJSONMinimal
- Fix contradictory package doc comment in parser.go to match the
  text-only tc parsing strategy
- Remove duplicate comment in parser_test.go, stale migration artifact
  in parser.go, and misleading reference in types.go
- Update README: bump Go version to 1.26, remove stale rtnetlink claims
- Use SplitLines instead of Split for text parsing, reanimating the
  existing utility function
- Add named constant for SSE retry interval
- Simplify dead ternary in interface count display
- Harden parseMemoryLine with parts[1] == "of" guard
- Bump go.mod and CI Go version to 1.26

Signed-off-by: Galih Tama <galpt@v.recipes>

Fix reverse-proxy frontend paths

docs: emphasize installer service activation in README

docs: clarify OpenWrt install notes (git-http, ca-bundle, wget compat…

…ibility)

Add OpenWrt hotplug startup fallback

Fix OpenWrt reboot startup race

Add OpenWrt install verification helper

Fix OpenWrt autostart service setup